Bead dispensing system

ABSTRACT

A bead dispensing system is provided for delivering small amounts of substances onto substrates. The system can include, for example, a movable support structure having an array of spaced-apart projections depending from its lower side. An attraction source, such as a vacuum, magnetic, and/or electrostatic force, is operable at each projection end region to attract and retain one bead. The projection array can be aligned with an array of bead-receiving regions of a substrate, e.g., an array of spaced-apart wells of a micro-plate or card. In one embodiment, a plurality of reagent-carrying beads are picked up, retained at respective projection end regions, and moved to a location over a multi-well plate. The beads are then released in a fashion permitting each bead to land in a respective well. The system of the invention is particularly useful for fabricating arrays of reagents.

[0001] This application is a Continuation-in-Part of U.S. applicationSer. No. 09/250,697 filed Feb. 16, 1999, now pending, which isincorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to the manipulation of small beadscapable of carrying substances such as reagents or samples, and thelike. More particularly, the invention provides a method and apparatusfor fabricating an array of such beads on a micro-card or plate.

BACKGROUND OF THE INVENTION

[0003] Multi-well arrays have long been popular for separatelyperforming numerous chemical and/or biological reactions atsubstantially the same time. Perhaps the most popular multi-well formatin recent years has been the 96-well microplate. Typically, severalmicroliters of reagents are placed in each of the 96 reaction wells, perassay. In an effort to decrease reagent costs, as well as to increasethroughput, many laboratory directors are now moving toward the use ofeven higher-density plates having very small wells, such as 384- and1536-well formats with wells about 1 millimeter in diameter, or smaller.With the higher density well formats, comes the need for distributingeven smaller amounts of substances (e.g. <1 μL) into extremely compactarrays.

[0004] Most conventional automated micro-volume deposition systemsdispense substances in fluid form, using robotic delivery assemblies. Ina typical system, a robot aspirates fluid into one or more ejectors,moves a loaded ejector to a well in a micro-card or plate, and deliversan aliquot of fluid. Commonly used ejectors include “non-contact”devices, such as ink jet nozzles, and “contact” devices, such as a pensor quills. Ink jets, pens, and quills are well-known devices used in avariety of applications. Unfortunately, for the purpose of depositingnumerous substances into the wells of a micro-card or plate, each ofthese devices is associated with certain disadvantages. For example, inkjets generally work fine when the fluid of interest has been carefullyoptimized for the nozzle. However, when depositing many different fluidsthrough the same nozzle, optimization for each separate fluid is oftenimpractical. As a result, the nozzles can become clogged. With regard topens and quills, these devices can collide with the well walls, and aregenerally too slow for cost-effective operations.

[0005] The task of delivering micro-volumes of fluidic substances can beespecially challenging when the substance deposited at each location isunique to one or only a few positions in the array. Furthercomplications can arise when multiple fluidic substances are seriallydeposited into each well. For example, liquids can drip and splatter,contaminating reagents in neighboring wells. As another disadvantage,all devices contacting a fluid reagent must be cleaned, or disposed of,before being used with a different fluidic reagent. This is necessary toprevent mixing (i.e., contamination) of one reagent with another. Itshould be appreciated that multiple rounds of cleaning and aspirationcan be time consuming and expensive, as well. This is especially truefor applications requiring a large number of different substances. As afurther disadvantage, it is often difficult to control the volume offluid dispensed with a high degree of accuracy. Also, small amounts ofdispensed liquid can be difficult to detect with standard imagingsystems. Accordingly, dispensing errors can go undetected and, thus,uncorrected.

[0006] The need is apparent for an apparatus and process capable offabricating an array of substances on a micro-card or plate in arelatively fast, efficient and accurate manner.

SUMMARY OF THE INVENTION

[0007] One aspect of the present invention provides a system for pickingup a plurality of relatively small beads from a supply and transferringthem to a desired location.

[0008] According to one embodiment, the system includes a plurality ofprojections, e.g., in the nature of tubes or rods, depending from asupport at spaced-apart locations defining an array. Each projection hasa lower end region, distal from the support, with a cavity formedtherein. Each such cavity is characterized by a lower opening, an upperceiling region, and a sidewall extending between the lower opening andupper ceiling region. An attraction source, such as a vacuum,electrostatic and/or magnetic force, is operable at each projection endregion in a manner effective to draw beads from the supply into thecavities and to releasably retain the beads therein.

[0009] In one embodiment, the sidewall about each cavity is formed, atleast in part, of a resiliently flexible material, such astetrafluoroethylene (TFE) tubing, or the like. The resiliently flexiblesidewall can have, for example, a generally cylindrical or tubularshape, with both an inner diameter and a longitudinal depth of less thanabout 1.5 mm. In an exemplary arrangement, intended for use withsubmillimeter beads, the inner diameter and longitudinal depth arebetween about 100-1,250 micrometers. In a particularly preferredconstruction, especially useful in connection with substantiallyspherical microbeads having a diameter of between about 275-325micrometers, the inner diameter and longitudinal depth are between about350-425 micrometers.

[0010] In an exemplary arrangement, the sidewall about each cavity has asubstantially constant inner diameter along a region extending betweenits lower opening and its upper ceiling region, such that linesextending longitudinally along confronting inner surfaces of eachsidewall are substantially parallel to one another.

[0011] According to one embodiment, the lower opening of each cavity hasa diameter of between about 100-1,250 micrometers. The longitudinallength of the sidewall, measured from the lower opening to the upperceiling, is preferably between about 0.50-1.25 times the diameter of thelower opening.

[0012] In another embodiment, the lower opening of each cavity has adiameter of between about 250-750 micrometers, and preferably betweenabout 350-425 micrometers. Further in this embodiment, the longitudinallength of the sidewall, measured from the lower opening to the upperceiling, is between about 0.75-1.10 times the diameter of the loweropening. In one particularly preferred embodiment, the diameter of thelower opening and the longitudinal length of the sidewall areapproximately equal.

[0013] In one embodiment, the cavity at the lower end region of eachprojection is configured to receive between about 0.50-1.25 beads, andpreferably between about 0.75-1.10 beads. In a particularly preferredembodiment, each cavity can receive one entire bead. The cavities, inthis preferred construction, are sized to preclude entry of asubstantial portion (e.g., >20%) of a second bead once a first bead hasto become situated therein.

[0014] The system of the present invention can further include aplurality of ampules for containing the bead supply. In a preferredarrangement, a plurality of plastic ampules are disposed in an arrayalignable with the projection array. Each ampule can be provided with acover member configured to extend over an upper opening thereof. Thecovers can be, for example, plastic domes or caps, and/or frangiblepolymeric membranes (films).

[0015] The support from which the projections depend can include, or beattached to, a frame adapted to pivot about a generally vertical axis,rendering the projection array movable along a generally arcuate orcircular pathway. The frame can further be adapted for reciprocal linearmotion along a generally vertical pathway. By this construction, theprojections can be aligned over the ampule array, and each projectioncan be lowered into a respective one of the ampules.

[0016] The ampules can hold any desired reagents. In one embodiment, forexample, each ampule holds beads carrying two primers, two probes andbuffer for use in real-time PCR. It should be appreciated that thereagents in the various ampules can be the same or different. In oneembodiment, one of the ampules holds a plurality of submillimeter beadsthat carry a first set of analyte-specific reagents, and another of theampules holds a plurality of submillimeter beads that carry a second setof analyte-specific reagents. The first and second reagent sets candiffer from one another, for example, by at least one analyte-specificcomponent.

[0017] The cavities at the lower end regions of the projections can beformed, for example, by fitting a resiliently flexible, tubular sleeve,or sheath, over their free ends such that an overhang region is leftextending below the terminal end of each projection. In thisconstruction, the overhand region can define the sidewall laterallybounding each cavity and the terminal end of each projection, facing thecavity, can define the upper ceiling region.

[0018] According to one embodiment, each of the projections is acapillary tube having an axial lumen extending therethrough. Each lumen,in this embodiment, is provided with a first end that opens into arespective one of the cavities through its ceiling region, and a secondend disposed in fluid communication with a pressure-control assembly.The pressure-control assembly can include, for example, a vacuum pumpoperable to establish a reduced pressure within each of the lumens,and/or a pump operable to establish an increased pressure within each ofthe lumens. Regarding the latter, such an increased pressure can beutilized to displace (blow out) any beads retained in the cavities.

[0019] In one preferred construction, each lumen is formed with an innerdiameter at its first end that is smaller than the diameter of arespective cavity into which it opens. For example, each cavity can havean inner diameter, at a location directly adjacent its ceiling region,of greater than 275 micrometers (e.g., between about 300-400micrometers), and each of the lumens can have an inner diameter at itsfirst end of between about 100-275 micrometers.

[0020] A detection system can be used to sense the presence or absenceof a bead retained in the various cavities. One embodiment, for example,provides a detection system having a field of view extending along eachof the projection end regions. In one particular arrangement, thedetection system includes a plurality of elongated light-conductive(optical) fibers. One end of each fiber, in this arrangement, extendsalong one of the projections and faces a respective cavity. The otherend of each fiber can be disposed in communication with a camera device,such as a CCD camera.

[0021] The system of the present invention can further include a conduitassembly having a plurality of conduits for separately guiding orfunneling a plurality of beads released from the various cavities todesired locations on a substrate (e.g., into wells of a micro-plate orcard). In one embodiment, the conduits have (i) large openings at theirupper ends disposed in an array having a center-to-center pitchsubstantially like that of the projection array such that the largeopenings are generally alignable thereunder, and (ii) small openings attheir lower ends.

[0022] The small openings can be disposed in an array having acenter-to-center pitch substantially like that of the large-openingarray, or the two arrays can differ in pitch. In one embodiment, forexample, the small openings are disposed in an array having acenter-to-center pitch substantially smaller than that of thelarge-opening array. In one particular arrangement, the center-to-centerpitch of the small-opening array is reduced by a factor of at leastabout 2, and preferably at least about 3, as compared to that of thelarge-opening array.

[0023] In one embodiment, the substrate onto which the beads aredeposited is a micro-plate or card having a plurality of wells disposedin an array alignable under the small-opening array of the conduitassembly. For example, the substrate can be a plastic 96-well plate. Theplate can be of standard dimensions, or custom dimensions. For example,the plate can have an 8×12 regular rectangular array of wells, with eachwell having a diameter, at its upper end, of about 1 mm.

[0024] The system can further include a detection system operable tosense the presence or absence of a bead in each well of a micro-plate orcard. In one embodiment, for example, a detection system is utilizedhaving a field of view extending through each of the conduits and downonto the substrate.

[0025] Another aspect of the present invention provides a system forchanneling a plurality of beads to desired locations on a substrate,such as a micro-plate or card.

[0026] According to one embodiment, the system includes an array of beadsupports, such as the previously described projections, with eachsupport being adapted to releasably hold, from above, no more than onebead. A plurality of conduits are disposed under the micro-bead supportarray. The conduits are provided with (i) large openings at their upperends disposed in an array having a center-to-center pitch substantiallylike that of the support array such that the large openings aregenerally alignable thereunder, and (ii) small openings at their lowerends.

[0027] In one embodiment, each of the large openings of the conduitassembly has a diameter of greater than about 1 mm (e.g., between 1-6mm), and each of the small openings has a diameter of less than about1mm (e.g., between 0.15-1 mm).

[0028] The small openings can be disposed in an array having acenter-to-center pitch substantially like that of the large-openingarray, or the two arrays can differ. In one embodiment, the smallopenings of the conduit assembly are disposed in an array having acenter-to-center pitch substantially smaller than that of thelarge-opening array. In an exemplary arrangement, the center-to-centerpitch of the small-opening array is reduced by a factor of at leastabout 2, and preferably at least about 3, as compared to that of thelarge-opening array. In another exemplary arrangement, thecenter-to-center pitch of the large-opening array is greater than about3 mm (e.g., between about 3-9 mm), and the center-to-center pitch of thesmall-opening array is less than about 3 mm (e.g., about 1-3 mm).

[0029] A parallelogram linkage assembly can be used to support theconduit assembly for reciprocal arcuate movement between a raisedposition, above and vertically offset from a substrate, and a loweredposition, directly over and in close proximity to a substrate. In onesuch embodiment, a parallelogram linkage assembly is supported on acarousel surface for pivotal movement radially of the carousel'srotational axis. A substrate holding area is also provided on thecarousel surface, radially outward of and adjacent to the parallelogramlinkage assembly. Further in this embodiment, a stationary rail extendsalong an inner region of the carousel, having a bearing surface inmechanical communication with the parallelogram linkage arrangement. Theconstruction is arranged to permit the parallelogram linkage assembly toride along the rail as rotational movement of the carousel advances it.In a preferred arrangement, the bearing surface includes a first arcuateregion disposed a first distance from the central axis at a firstvertical height, and a second arcuate region disposed a second distancefrom the central axis at a second vertical height. In this arrangement,the second distance is shorter than the first distance, and the secondvertical height is higher than the first vertical height. When theparallelogram linkage arrangement rides along the first arcuate region,the conduit assembly assumes the lowered position over the substrateholding area. When the parallelogram linkage arrangement rides along thesecond arcuate region, on the other hand, the conduit array assumes theraised position. The bearing surface can also include transition regionsbridging the first and second arcuate regions.

[0030] According to one embodiment, the substrate is a micro-plate orcard having a plurality of wells disposed in an array alignable underthe small-opening array of the conduit assembly. For example, thesubstrate can be a plate having 96 wells, or more. The micro-plate orcard can include a pair of spaced-apart indexing bores and/or slots(holes), with each being configured for alignment with a respectiveindexing pin depending from a lower side of the conduit assembly. Uponinserting the indexing pins into the indexing bores or slots, theconduit assembly's small-opening array becomes substantially alignedwith the substrate's array of wells.

[0031] In one embodiment, a detection system is provided having a fieldof view extending into each of the conduits of the conduit assembly. Thedetection system, in this embodiment, is adapted to sense the presenceor absence of a bead on the micro-plate or card under each of the smallopenings. In an exemplary arrangement, the detection system includes aradiation source, such as a laser, adapted to illuminate the micro-plateor card at locations, e.g., wells, below each of the small openings. Thesystem can further include a plurality of elongated light-conductive(optical) fibers, with each fiber having one end facing, or extendinginto, a respective one of the large openings to receive light travelingup through a respective conduit and a second end communicating with acamera device, such as a CCD camera.

[0032] In another of its aspects, the present invention provides asystem for covering an array of wells formed in a micro-plate or card.

[0033] According to one embodiment, the system includes a web of anoptically clear cover material mounted for movement from a supply reelto a take-up reel. Shearing blades are mounted for reciprocal linearmotion along a direction substantially normal to the web for cutting outa portion of the cover material at a region between the supply andtake-up reels. A resiliently compliant, generally planar surface isprovided between the blades for pressing the web against the uppersurface of the micro-card, over the wells.

[0034] In one embodiment, a pair of indexing pins extends below thecompliant surface. Further in this embodiment, the micro-card isprovided with a pair of spaced-apart indexing bores or slots, with eachbeing alignable with one of the indexing pins. Registration of theindexing pins with the bores or slots serves to orient the shearingblade over the micro-card for effecting a cut in the web. In a relatedembodiment, the shearing blade has a cutting edge defining aquadrilateral, such as a square or rectangle. Upon registering theindexing pins with the indexing bores, a cut can be made in the webhaving (i) two sides substantially parallel to the side edges of the weband (ii) two sides substantially normal to the side edges of the web.Preferably, the web has a side-to-side width that is longer than the cutalong the direction normal to the side edges of the web, so that the webis not severed in two upon making the cut.

[0035] A further aspect of the present invention provides an apparatusfor delivering a substance (e.g., a liquid solvent or reagent) onto asubstrate.

[0036] In accordance with one embodiment, the apparatus includes aplurality of elongated conduits disposed in fixed, spaced relation in acommon support structure. The support structure can be, for example, ablock, tray, plate, frame or the like. In one embodiment, the supportstructure is made substantially of glass. Each of the conduits isprovided with a large opening at one end and a small opening at itsother end. Between its two ends, each conduit can have a tapered orfunnel-shaped region. The large openings are disposed in an array alongone side of the support structure, and the small openings are disposedin an array along an opposite side of the support structure. The large-and small-opening arrays can be arranged with a similar pitch(center-to-center spacing), or they can differ. In one embodiment, thelarge-opening array is arranged with a center-to-center pitchsubstantially larger (e.g., greater than about 2:1, and preferablygreater than about 3:1) than that of the small-opening array.

[0037] In one preferred arrangement, a region of each conduit extendingfrom a respective one of the small openings is of capillary size, suchthat a liquid placed in contact with the small-opening array can bedrawn at least partially into each conduit. For example, thecapillary-size region of each conduit can have an inner diameter of lessthan about 1 mm. In one embodiment, the capillary-size region of eachconduit is provided with an inner sidewall that is hydrophilic.

[0038] In yet another of its aspects, the present invention provides amethod for simultaneously transferring a plurality of beads from onelocation to another location.

[0039] According to one embodiment, the method includes the steps of:

[0040] (i) picking up, in a substantially simultaneous fashion, aplurality of beads from a supply and retaining the beads at respective,spaced-apart locations defining an array;

[0041] (ii) releasing the beads, in a substantially simultaneousfashion, over a substrate having an array of separate bead-holdingregions; and

[0042] (iii) individually channeling or guiding each of the releasedbeads, in a substantially simultaneous fashion, to a respective one ofthe bead-holding regions.

[0043] The step of picking up beads can be effected, for example, byestablishing a reduced pressure (vacuum) at each of the locations, andthe step of releasing the beads can be effected by establishing anincreased pressure (positive gas flow) at each of the locations.

[0044] In one embodiment, the array of bead-holding regions (e.g., wellsof a micro-plate or card) has a center-to-center pitch substantiallysmaller than that of the retained-bead array. In an exemplaryarrangement, the center-to-center pitch of the array of bead-holdingregions is reduced by a factor of at least about 2, and preferably atleast about 3, as compared to that of the retained-bead array.

[0045] According to one embodiment the bead supply is provided in anarray of plastic capsules or ampules. A cover can be provided over anupper opening of each ampule. The covers can be removed, or punctured,to provide access to the beads. Suitable covers can include, forexample, polymeric film-like membranes, or plastic caps/domes.

[0046] One embodiment provides, between step (i) and step (ii), a stepof inspecting each location of the retained-bead array for the presenceof a bead; and picking up and retaining a bead for locations lacking abead. After step (iii), each of the bead-holding regions can beinspected for beads deposited therein.

[0047] In one embodiment, each of the bead-holding regions can becovered with an optically clear film, or the like. The film can besealed over the bead-holding regions using adhesives and/or heat-sealingtechniques.

[0048] These and other features and advantages of the present inventionwill become clear from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The structure and manner of operation of the invention, togetherwith the further objects and advantages thereof, may best be understoodby reference to the following description taken in conjunction with theaccompanying drawings, in which:

[0050]FIG. 1 is a partially schematic side elevational view, withportions shown in phantom, of a system for fabricating an array ofreagent-carrying beads on a substrate, constructed in accordance withone embodiment of the present invention.

[0051]FIG. 2 is a side elevational view, with portions shown in phantom,of an ampule containing a plurality of reagent-carrying beads, andhaving a dome-like cover member over an upper opening, according to anembodiment of the present invention.

[0052]FIG. 3(A) is a side elevational view, with portions shown inphantom, of an ampule containing a plurality of reagent-carrying beads,and having a film-like cover member over an upper opening, according toa further embodiment of the present invention.

[0053]FIG. 3(B) is a side elevational view of the ampule of FIG. 3(A),further showing an elongated projection, in the nature of a tube, thathas punctured the cover member to gain access to the beads containedtherein, as taught by an embodiment of the present invention.

[0054]FIG. 4(A) is a side elevational view, with a portion broken awayand others shown in phantom, of an elongated projection, in the natureof a tube, for use in attracting and retaining reagent-carrying beads,according to an embodiment of the present invention.

[0055]FIG. 4(B) is a side elevational view of the projection shown inFIG. 4(A), further illustrating a bead disposed in a cavity at the lowerend region of the projection.

[0056]FIG. 5 is a side cross-sectional view of one preferredconstruction for a projection useful in attracting and retainingreagent-carrying beads, as taught by an embodiment of the presentinvention.

[0057]FIG. 6 is a partial view of the system depicted in FIG. 1,illustrating the simultaneous removal of a plurality of dome-like covermembers from a like number of ampules containing a bead supply,according to an embodiment of the present invention.

[0058]FIG. 7 is a side elevational view, with portions shown in phantom,of a projection, in the nature of an elongated tube, having aresiliently flexible lower end region that can bend when pressed againstthe bottom region of an ampule, in accordance with an embodiment of thepresent invention.

[0059]FIG. 8A is a side cross-sectional view of an array of projections,like that of FIG. 1, with each projection having an optical fiberextending therethrough for determining the presence of a bead in arespective cavity at its lower end region, according to an embodiment ofthe present invention.

[0060]FIG. 8B a top view of a horizontal crossbar and bead extractors ofthe system shown in FIG. 1, with portions of the bead extractors brokenaway in the phantom-depicted positions to illustrate cameras employed tocapture an image of the lower end of a projection array for determiningthe presence or absence of a target object, according to an embodimentof the invention.

[0061]FIG. 8C is a schematic view of a display device, which may be usedin connection with the cameras shown in FIG. 8B, for displaying an imageof the lower end of a projection array.

[0062]FIG. 9 is a partially schematic side elevational view, withportions shown in phantom, of a system for fabricating a micro-array ofreagent-carrying beads on a substrate, constructed in accordance with anembodiment of the present invention.

[0063]FIG. 10(A) is a side cross-sectional view of a conduit assemblyhaving an array of conduits configured for separately directing aplurality of beads into the wells of a micro-plate or card, inaccordance with an embodiment of the present invention.

[0064]FIG. 10(B) is a top plan view of the conduit assembly of FIG.10(A), showing an array of large openings of the conduits.

[0065]FIG. 10(C) is a plan view from beneath the conduit assembly ofFIG. 10(A), showing an array of small openings of the conduits, as wellas a pair of indexing pins on either side of the small-opening array.

[0066]FIG. 11 is a partially schematic side elevational view, withportions depicted in phantom, of a parallelogram linkage assembly forreciprocally moving a conduit assembly between a raised position, shownin dashed lines, and a lowered position over a bead-receiving substrate,shown in solid lines, in accordance with an embodiment of the presentinvention.

[0067]FIG. 12(A) is a top plan view of a multi-well micro-card having anindexing bore formed along one side and an indexing slot formed along anopposing side, according to the teachings of the present invention.

[0068]FIG. 12(B) shows, in side-sectional view, the multi-well card ofFIG. 12(A) resting on a substrate-holding area, and a pair of indexingpins extending from a conduit assembly passed through the bore and slotof the card, in accordance with an embodiment of the present invention.

[0069]FIG. 13 is a perspective view of a high-throughput system forfabricating an array of beads on a micro-plate or card, according to onepreferred embodiment of the present invention.

[0070]FIG. 14 is a partially schematic side-sectional view of adetection system for determining the presence of beads at bead-receivinglocations of a substrate, in accordance with an embodiment of thepresent invention.

[0071]FIG. 15 is a partially schematic side-sectional view of adetection system, similar to that of FIG. 14, further including an arrayof optical fibers configured to extend down into the conduits of aconduit assembly positioned over a bead-receiving substrate, accordingto a further embodiment of the present invention.

[0072]FIG. 16(A) is a partially schematic side-sectional view of asystem for covering an array of wells formed in a substrate, such as amicro-plate or card, with a film-like cover material, according to anembodiment of the present invention.

[0073]FIG. 16(B) is a top plan view of a length of cover material on atake-up reel of the device of FIG. 16(A), showing areas that have beencut out for use in covering the wells of substrates, in accordance withthe teachings of the present invention.

[0074]FIG. 17(A) is a side elevational view, with portions shown inphantom, of a hand-operable system for fabricating an array ofreagent-carrying beads on a multi-well plate, constructed in accordancewith an embodiment of the present invention.

[0075]FIG. 17(B) is a top plan view, with portions shown in phantom, ofthe hand-operable system of FIG. 17(A).

[0076]FIG. 18 is a side cross-sectional view of a fluid distributorhaving an array of conduits for transferring a liquid from a vessel toan array of wells of a micro-plate or card, according to an embodimentof the present invention.

[0077]FIG. 19(A) is a perspective view showing an array of smallopenings, surrounded by a channel, formed in one side of the fluiddistributor of FIG. 18.

[0078]FIG. 19(B) is a perspective view showing an array of largeopenings, surrounded by an upstanding peripheral wall, formed on oneside of the fluid distributor of FIG. 18.

[0079]FIG. 20 is a side cross-sectional view of the fluid distributor ofFIGS. 18-19 disposed over a vessel containing a liquid, and showingportions of the liquid drawn partially into the conduits of the fluiddistributor by capillary action, in accordance with the teachings of thepresent invention.

[0080]FIG. 21 (A) is a side cross-sectional view of the fluiddistributor of FIGS. 18-20 inverted over a multi-well plate, showingaliquots of liquid that have traveled downward through respectiveconduits to form drops at each of the large openings, over respectivebead-containing wells of the plate.

[0081]FIG. 21 (B) is a perspective view of the multi-well plate shownunder the fluid distributor in FIG. 21(A).

[0082]FIG. 22 is a side cross-sectional view of the inverted fluiddistributor of FIG. 21(A), with the drops having been pulled into thewells of the multi-well plate due to adhesive forces with the beads.

DETAILED DESCRIPTION OF THE INVENTION

[0083] The following discussion of the preferred embodiments of thepresent invention is merely exemplary in nature. Accordingly, thisdiscussion is in no way intended to limit the scope of the invention.

[0084] One aspect of the present invention provides a system for pickingup a plurality of small, reagent-carrying beads from a supply or sourcearea and transferring them onto a substrate, e.g., wells in a micro-cardor plate. Generally, the system includes a plurality of projectionsdepending from a movable support structure at fixed, spaced-apartlocations. A cavity is provided at a lower end region of each of theprojections, defined by a (i) lower opening, (ii) an upper ceiling, and(iii) a sidewall extending between the lower opening and upper ceiling.An attraction source is operable at each of the projection end regionsin a manner effective to draw individual beads from the supply intorespective cavities and to releasably retain them therein. Whileretained in the cavities, the beads can be moved from one place toanother with movement of the support structure. Once the beads have beenpositioned at a desired location, they can be released from thecavities. A plurality of conduits can be used to separately guide orchannel the beads, once released from the cavities, to desired locationson the substrate.

[0085] More particularly, and with initial reference to the exemplaryembodiment of FIG. 1, a reagent supply is indicated at 12, having aplurality of spaced-apart reagent-supply locations, arranged in anarray. Each reagent-supply location is defined by a well, such as 16a-16 f, of a reagent plate 20. While only six such locations, arrangedside-by-side in a linear fashion, are visible in the view of FIG. 1, itshould be understood that any reasonable number of supply locations canbe disposed in any desired spatial configuration. For example, a reagentplate, like plate 20, can include 24, 48, 96, 384, 1024, 1536 wells, ormore, with each well being configured to support a plurality ofreagent-carrying beads. In such arrangements, the wells will typicallybe arranged in a regular array, e.g., an 8×12, 16×24, 32×32, or a 32×48rectangular array, though other layouts are possible. As indicatedabove, each reagent-supply location 16 a-16 f can hold a plurality ofbeads, such as 24 a-24 f, respectively. Each bead, in turn, can carry adesired reagent.

[0086] A wide variety of reagent-carrying beads can be used with thepresent invention. Generally, the beads should resist substantialphysical deformations when exposed for a relatively short time tomoderately stressful conditions, e.g., being pulled upon by anattractive force such as a vacuum, or a magnetic or electrostatic field,as discussed more fully below. Certain embodiments, for example,contemplate the use of beads having a substantially rigid outer shell,or a soft gelatinous coating. Several exemplary types of beads aredescribed next.

[0087] In one embodiment, the beads are formed by applying a coatingmaterial, such as a gelatin, to a reagent core. The coating cures toform a substantially solid shell about the reagent. The coating can bedissolvable or swellable to permit access to the reagent undercontrollable conditions (e.g., upon exposure to a particular solvent).Guidance for preparing coated beads, or micro-particles, is provided,for example, in: [1] R. Pommersheim, H. Lowe, V. Hessel, W. Ehrfeld(1998), “Immobilation of living cells and enzymes by encapsulation,”Institut für Mikrotechnik Mainz GmbH, IBC Global Conferences Limited;[2] F. Lim A. Sun (1980), Science 210, 908; [3] R. Pommersheim, JSchrezenmeir, W. Vogt (1994), “Immobilization of enzymes and livingcells by multilayer microcapsules” Macromol Chem. Phys 195, 1557-1567;and [4] W. Ehrfeld, V. Hessel, H. Lehr, “Microreactors for ChemicalSynthesis and Biotechtechnology-Current Developments and FutureApplications” in: Topics in Current Chemistry 194, A. Manz, H. Becker,Microsystem Technology in Chemistry and Life Science, Springer Verlag,Berlin Heidelberg (1998), 233-252; each expressly incorporated herein byreference.

[0088] In another embodiment, a plurality of bead-like particles act assolid supports for the reagents. For example, reagents can besynthesized on the beads, or absorbed thereto. In still a furtherembodiment, a slurry or dispersion comprised of a reagent and bindingmaterial is used to form a plurality of bead-like particles, with eachindividual bead having a substantially homogenous consistency. Methodsfor preparing such beads are well known to those skilled in the art.

[0089] A plurality of different reagents can be formed into respectivecollections or groups of reagent beads, referred to herein as “lots.”For example, 10,000 different reagents can be formed into 10,000different bead lots, with each lot comprised of a plurality ofsubstantially like beads carrying a respective reagent. To assist indistinguishing beads from different lots, and to provide a means forquickly determining the type of reagent carried by any one particularbead, beads from each lot can be formed to display a particular,pre-assigned color. For example, yellow beads can carry reagent “A,”blue beads can carry reagent “B,” and red beads can carry reagent “C.”Beads from each lot can be placed at respective reagent-supplylocations.

[0090] In one embodiment, a plurality of bead lots are formed, whereineach bead includes a reagent core covered with a coating material, suchas a gelatin, having well-defined physical and chemical properties.Preferably in this embodiment, all beads in all lots bear substantiallythe same outer coating (i.e., a “generic” coating), with the coatingsfor each lot differing only in color, as discussed above. It should beappreciated that this arrangement reduces the risk of equipmentcontamination due to contact with the reagents themselves. If anyresidues are left behind as the reagents move through the system, suchresidues will all be of the same, known coating material. Preferably,the coating material is chosen so that any residues are innocuous to thesystem. It should further be appreciated that a higher speed fordepositing substances can be achieved using such beads, as compared toconventional liquid deposition systems, because the hardware deliveringthe beads will not require frequent cleaning, nor is time spentaspirating fluids.

[0091] While beads of substantially any shape can be used with thepresent invention, beads having a generally spherical geometry areparticularly well suited for use herein. Also, the system of theinvention can be used with beads of various sizes. For example, oneembodiment contemplates the use of spherical beads having a diameter ofless than about 1 mm. In one such arrangement, each bead is formed witha diameter of between about 275-325 micrometers, and most preferablyabout 300 micrometers. In another embodiment, the beads are larger, suchthat each bead substantially fills one well of the reagent plate. Forexample, each bead can have a diameter of between about 1.0-4.0 mm, andpreferably about 3.7 mm. Each well of the reagent plate, in turn, can beconfigured with an inner diameter slightly larger than the diameter of abead. The lower end of each well, in this embodiment, can be shaped tocomplement the contour of the bead's outer surface.

[0092] The beads can carry any desired reagent. As used herein, the term“reagent” can refer to a single substance, or a grouping of substances.According to one preferred embodiment, the reagent carried by each beadincludes components useful for real time fluorescence-based measurementsof nucleic acid amplification products (such as PCR) as described, forexample, in PCT Publication WO 95/30139 and U.S. patent application Ser.No. 08/235,411, each of which is expressly incorporated herein byreference.

[0093] In an exemplary arrangement, each bead carries ananalyte-specific reagent effective to react with a selected analyte thatmay be present in a sample. For example, for polynucleotide analytes,the analyte-specific reagent can include first and secondoligonucleotide primers having sequences effective to hybridize toopposite end regions of complementary strands of a selectedpolynucleotide analyte segment, for amplifying the segment byprimer-initiated polymerase chain reaction. The analyte-specificdetection reagent can further include a fluorescer-quencheroligonucleotide capable of hybridizing to the analyte segment in aregion downstream of one of the primers, for producing a detectablefluorescent signal when the analyte is present in the sample.

[0094] A plurality of beads from the same or substantially identicallots can be packed into an ampule or capsule. A plurality of suchampules (e.g., tens, hundreds, thousands, or more) can be dispensed intorespective, designated wells of a multi-well plate, with the variousampules containing the same or different reagents, as desired. Asdepicted in FIG. 1, for example, a plurality of plastic ampules 26 a-26f, each holding beads carrying a different reagent, are removably seatedin respective wells, 16 a-f, of reagent plate 20. Ampules of any desiredsize and shape can be used. One arrangement, for example, contemplatesthe use of generally bullet-shaped ampules having an open top and arounded, closed bottom. Exemplary dimensions for each ampule are asfollows: (i) about 10 mm in height, (ii) an outer diameter of about 3.7mm, and (iii) an inner diameter of about 3.0 mm. About 1,000substantially spherical reagent beads, each having a diameter of about300 micrometers, can be loaded into each such ampule. An exemplaryreagent plate, useful for holding the just-described ampules, isconfigured with an array of wells (e.g., an 8×12, 16×24, or 32×32array), with each well having an inner diameter of about 4.0 mm and adepth of between about 6-9 mm.

[0095] The ampules can be placed in the wells of the reagent plate inany suitable manner. In one embodiment, an operator manually places theampules in the wells. In another embodiment, the ampules are seriallydispensed from respective containers supported in an array of holdingcells disposed above the reagent plate, as taught in U.S. applicationSer. No. 09/251,232 filed Feb. 16, 1999 and expressly incorporatedherein by reference.

[0096] Each ampule can be provided with a cover member over an upperopening thereof. The cover member can be, for example, a removable capor dome, such as 30 a of FIG. 2, having an open end 32 a configured tofit snugly about an opening defined by an upper rim, or lip, 28 a of anampule 26 a. Or, a sheet-like film or membrane, such as 34 a of FIG.3(A), can be applied to an upper rim 28 a about the opening of an ampule26 a. For example, a polymeric film, such as a polystyrene, polyester,polypropylene or polyethylene film, between about 0.05-0.40 millimetersthick, can cover the upper opening of each ampule. In one embodiment,the cover is a thin polyvinylidene chloride (PVDC) film, such as thatsold under the trade name SARAN WRAP by Dow Chemical Co., (Midland,Mich.).

[0097] As described more fully below, access to the beads can be gained,for example, by displacing the covers using the projection array.

[0098] In one embodiment, the cover member over each ampule forms asubstantially airtight seal, sequestering the contents of the ampulefrom the external atmosphere. The seal can be effected or enhanced, forexample, using conventional adhesives, elastomers and/or byheating-sealing techniques. In an exemplary arrangement, frictionalengagement between a plastic dome-shaped cap and the upper region of aplastic ampule is sufficient to provide an airtight seal. The sealedampules can further contain an inert gas, such as nitrogen or the like,surrounding the beads.

[0099] In another embodiment, each cover member is primarily designed toprevent against spillage, or other loss, of a respective ampule'scontents. In this embodiment, the interface between each cover memberand its respective ampule is not necessarily airtight.

[0100] To prevent against inadvertent dislodgment of the seated ampules,means can be provided for holding the ampules in place at eachreagent-supply location. For example, FIG. 1 shows a vacuum manifold,indicated generally at 40, formed in plate 20 under wells 16 a-16 f.Manifold 40 includes a plurality of generally vertical passageways thatcommunicate a central chamber of the manifold with the bottom regions ofrespective wells 16 a-16 f. It should be noted that the uppermost end ofeach vertical passageway, which opens into a respective well, has asmaller diameter than the outer diameter of a seated ampule. Apressure-control source, such as vacuum pump 44, is disposed in fluidcommunication with a lower region of manifold 40 by way of a connectorline, denoted as 46. Upon activating pressure-control source 44, areduced pressure can be established at the bottom region of each well 16a-16 f. The reduced pressure is effective to draw upon the bottom ofeach seated ampule 26 a-26 f, thereby preventing dislodgment from thewells. Upon deactivating pressure-control source 44, the ampules can bereadily removed from the wells, if desired.

[0101] Instead of loading the beads into an ampule or capsule, which isthen placed at a reagent-supply location, one embodiment contemplatesplacement of the beads directly into the wells, or other holding areas,of a reagent plate or the like. The wells of the reagent plate, in thisembodiment, can be formed with fully closed bottoms.

[0102] With continuing reference to the embodiment of FIG. 1, a pair ofbead extractors, denoted generally by the reference numerals 50 a and 50b, are adapted for positioning at respective locations that are elevatedwith respect to reagent plate 20. Each extractor 50 a, 50 b includes aplurality of projections, such as 54 a-54 f and 54 g-54 l, dependingfrom a respective support structure, 58 a and 58 b, at fixed,spaced-apart locations. Each projection can be shaped, for example, asan elongated nub, tube, rod, or the like, extending from the support.Preferably, the longitudinal axes of projections 54 a-54 f, 54 g-54 lare disposed such that they are generally parallel to one another.

[0103] Projections 54 a-54 f, 54 g-54 l can be formed integrally withtheir respective support structures 58 a, 58 b, or they can be formedseparately and attached by any suitable means. According to oneembodiment, for example, a plurality of separately-formed projectionsbear threads at one end for mating engagement with respective threadedbores extending into the lower side of a respective support.

[0104] Together, each group of projections 54 a-54 f, 54 g-54 l definesa respective projection array, denoted as 56 a and 56 b. Each projectionarray 56 a, 56 b is configured with substantially the samecenter-to-center spacing as the array of reagent-supply locations(wells) 16 a-16 f in reagent plate 20. Preferably, each projection array56 a, 56 b includes as many projections as the reagent plate hasreagent-supply locations, or a substantial fraction thereof. By thisconstruction, each projection array 56 a, 56 b is alignable withlocations of the supply.

[0105] A substantially T-shaped frame, denoted generally as 60, supportsboth extractors 50 a, 50 b. More particularly, frame 60 includes anupper, horizontal Where a tube already having a longitudinally extendingbore or lumen, such as at 86 a in FIG. 4(A), is used, cavity 70 can beformed by drilling a counterbore into an end of the tube, with thecounterbore having a diameter greater than the inner diameter of thelumen 86 a, yet smaller than the outer diameter of the tube.

[0106] The cavity at the end region of each projection is preferablyconfigured to receive no more than about one entire bead. FIG. 4(B), forexample, shows a single bead 24 a contained within cavity 70. Notably,in this embodiment, cavity 70 is substantially filled by bead 24 a,leaving insufficient room to accommodate a second entire bead, or even asubstantial portion of a second bead. It should be appreciated that theparticular size of the cavity will generally be determined by the sizeof the beads used with the system. Thus, for substantially sphericalbeads a little less than 1 mm in diameter (e.g., 0.75-0.95 mm), asuitably sized cavity can have an inner diameter, from one sidewallregion to a directly opposing sidewall region, of about 1 mm. Thelongitudinal depth, from the ceiling region to the lowermost opening,will generally be from between about 50%-125% of the size of the innerdiameter of the cavity. Accordingly, in this example, the longitudinaldepth is between about 0.50-1.25 mm. Preferably, the longitudinal depthis between about 75%-100% of the cavity's inner diameter; and mostpreferably the longitudinal depth and inner diameter are approximatelyequal. In a particularly preferred embodiment, wherein substantiallyspherical beads having a diameter of between about 275-325 micrometersare utilized, each cavity is configured with both an inner diameter andlongitudinal depth of between about 330-500 micrometers, and mostpreferably about 375 micrometers. The cavity, in this embodiment, isformed at the end of a polyurethane rod or tube having an outer diameterof about 0.5 mm.

[0107]FIG. 5 shows one preferred construction for a projection, denotedgenerally as 54 a′, for use in a projection array, such as 56 a and 56 bof FIG. 1. In this embodiment, each cavity 70′ is formed, for example,by fitting a hollow sheath, or sleeve, 80 over the end of an elongatedtube or rod 82, and leaving an overhang region of the sheath, as at 80a, extending below a terminal end 82 a of the tube. In this arrangement,the overhang region 80 a of sheath 80 defines sidewalls 76′, and theterminal end 82 a of the tube 82, facing cavity 70′, defines a ceilingregion 74′. Frictional engagement of sheath 80 about the end of tube 82can maintain the relative positioning of these elements. Optionally,conventional adhesives, abrasives, and/or shrink-fitting techniques canbe used to hold sheath 80 in place on tube 82. Tube 82 can beconstructed, for example, of a substantially rigid material, such asglass, plastic, metal, and the like. Sheath 80 can be formed, forexample, from a material that is resiliently expandable and flexible,such as tetrafluoroethylene (TFE), or the like. Suitable tubing, for usein constructing sheath 80, is available commercially, for example, fromMcMaster-Carr Supply Co. (Chicago, Ill.) under the product name“Thinwall Teflon TFE Spaghetti Tubing.”

[0108] The ceiling region 74 can have any suitable shape or contour. Inthe exemplary arrangement of FIG. 4(A), ceiling region 74 is generallyconical or funnel-shaped, with an inwardly and upwardly sloped surface(along the direction away from the lower end of the tube). In a similararrangement (not shown), the ceiling region is generally horn-shaped. Instill a further embodiment, the surface of the ceiling region issubstantially planar, as shown, for example, at 74′ in FIG. 5.

[0109] As previously indicated, an attraction source is operable at eachof the projection end regions in a manner effective to draw individualbeads from the supply into respective cavities and to releasably retainthem therein. In a typical operation, the attraction source will beengaged after an array of projections, such as 56 a or 56 b (FIG. 1),has been aligned with a corresponding array of reagent-supply locations,such as wells 16 a-16 f, and the projections have been lowered torespective positions proximate a plurality of reagent beads, such as 24a-24 f, held therein. The attraction source can be, for example, areduced pressure (vacuum), an electrostatic force, and/or a magneticforce. In one preferred embodiment, the attraction source is a vacuum.In the embodiment of FIG. 1, for example, each of the projections, 54a-54 f and 54 g-54 l, is a capillary tube having an axial lumen,respectively denoted as 86 a-86 f and 86 g-86 l, extending therethrough.As best seen in the detailed view of FIGS. 4(A)4(B), lumen 86 a providesa passageway for a vacuum to extend longitudinally through theprojection 54 a. Lumen 86 a has a lower end that opens into a respectivecavity 70 through a central area of ceiling 74. At its lower end, theinner diameter of lumen 86 a is smaller than the diameter of cavity 70,at a location adjacent the ceiling region 74. In an exemplaryarrangement, each of the cavities has a diameter of at least 275micrometers (e.g., between about 300-350 micrometers, and preferablyabout 325 micrometers), and each of the lumens has an inner diameter atits lower end of less than 275 micrometers (e.g., between about 230-270micrometers, and preferably about 250 micrometers).

[0110] In an alternative embodiment, a plurality of beads are attractedto, and retained at, respective projection end regions usingelectrostatic means. Techniques for attracting and retaining micro-beadsusing an electrostatic force are disclosed, for example, in U.S. Pat.Nos. 5,788,814 and 5,846,595; each of which is expressly incorporatedherein by reference.

[0111] Referring again to FIG. 1, the upper end of each lumen 86 a-86 f,86 g-86 l leads to a respective manifold, such as 88 a and 88 b, formedin support structures 58 a, 58 b. Each manifold 88 a, 88 b, in turn, isdisposed in fluid communication with a respective pressure-controlsource. For example, manifold 88 a can communicate with vacuum pump 94via flow line 92 a, and manifold 88 b can communicate with vacuum pump96 via flow line 92 b. Each vacuum pump 94, 96 is operable, e.g., underthe direction of a control computer (not shown), to establish a reducedpressure in a respective line 92 a, 92 b and, consequently, within arespective array of lumens 86 a-86 f, 86 g-86 l.

[0112] The manifolds can be of a generally monolithic construction,e.g., molded of plastic or metal; or they can be assembled fromsub-component parts. Regarding the latter, one embodiment (not shown)contemplates a manifold comprised of several sub-component layers,stacked one on top of the other. One such multi-layered arrangementincludes a rectangular frame member, having a central opening,sandwiched between upper and lower rectangular plate members. Together,the layers form a box-like structure having a central open region, orchamber. Particularly, the upper surface of the lower plate memberdefines a floor region; the inner edge of the rectangular frame memberprovides lateral sidewalls; and the lower surface of the upper platemember defines a ceiling region. A rectangular gasket can be interposedbetween confronting regions of the frame member and each plate member topromote airtight interfaces. The lower plate can be formed with an arrayof bores extending fully between its two broad surfaces. Each bore canbe suitably threaded to receive, from below, a threaded end of arespective tubular projection, and to communicate a lumen extendinglongitudinally through such projection with the region (chamber) abovethe plate. Conventional washers and/or gaskets can be used to promote anairtight interface between each projection and the lower plate. Theupper plate, which can be attached to a rotatable frame, such as 60, canhave one or more conduits formed therethrough for communicating the mainchamber with a like number of remotely positioned pressure-controlsources.

[0113] In an exemplary operation, wells 16 a-16 f of reagent plate 20are loaded with respective ampules 26 a-26 f, each of which contains aplurality of beads 24 a-24 f carrying a particular reagent. A projectionarray, such as 56 a, is then aligned with the array of wells 16 a-16 fin plate 20. This can be accomplished, for example, by placing reagentplate 20 at a location underlying the arcuate or circular pathway alongwhich the array 56 a moves when the central vertical shaft 60 c of frame60 is rotated about its longitudinal axis. Rotational motor 64 can thenrotate frame 60 until array 56 a assumes a position directly over, andin alignment with, the ampules 26 a-26 f of plate 20. Next, linear motor66 can lower the projections 54 a-54 f toward respective ampules 26 a-26f.

[0114] If the ampules are provided with cover members, such as dome 30 a(FIG. 2) or film 34 a (FIG. 3(A)), then the cover members must bedisplaced from the opening region of each ampule, at least partially, inorder to access the beads therein. With regard to film-type covers,e.g., a thin polymeric membrane, as the projections 54 a-54 f arelowered, each can engage and rupture the cover, as exemplified in FIG.3(B). In this way, all of the covers in the array can be displaced atsubstantially the same time.

[0115] An exemplary process for removing cap or dome-type covers isdepicted in FIG. 6. This process is particularly useful forsimultaneously removing a plurality of covers that are frictionallyfitted about the upper rim or lip region of respective ampules; thefrictional engagement being such that each cover and ampule can bepulled apart using only a moderate amount of force. Projections 54 a-54f are lowered until each engages the top of a respective dome-type cover30 a-30 f. Pressure-control source 44 is actuated to generate a reducedpressure in flow line 46 and, thus, in manifold 40 and at the lowerregions of wells 16 a-16 f. Pressure-control source 94 is actuated togenerate a reduced pressure in flow line 92 a and, thus, in manifold 88a and at the lower regions of projections 54 a-54 f. Responsive to thevacuum forces, the bottom of each ampule is drawn downward against thelower region of its respective well, and the top of each cover member isdrawn up against a lower rim or lip of a respective projection.

[0116] Maintaining a vacuum hold on the domes, projections 54 a-54 f canbe lifted, as exemplified in FIG. 6, thereby pulling domes 30 a-30 f offof, and away from, ampules 26 a-26 f and exposing beads 24 a-24 f. Oncethe domes have vertically cleared the ampules, rotational motor 64 canrotate frame 60 until the domes are positioned over a depository area(not shown). At this point, the vacuum can be discontinued, permittingthe covers to fall, for example, into a collection container (notshown). Rotational motor 64 can then rotate the projection array backinto alignment with the ampule array.

[0117] Referring again to FIG. 1, once the covers have been removed, orin the event that no covers are utilized, the projections 54 a-54 f canbe lowered to respective positions proximate the beads 24 a-24 f in thevarious ampules 26 a-26 f. Pressure-control source 94 can be actuated togenerate a vacuum reaching through each of lumens 86 a-86 f to arespective cavity, such as cavity 70 of FIGS. 4(A)-4(B), at the lowerend region of each projection. The vacuum force that is established atthe lower end region of each projection is sufficiently strong toattract a reagent bead from a respective ampule 26 a-26 f, and to retainthe bead in a cavity of the projection. In one embodiment, for example,a pressure of about 15 psi is established at each projection end regionto attract and retain spherical beads, each about 300 micrometers indiameter, in a cavity measuring about 325 micrometers in diameter andlongitudinal depth.

[0118]FIG. 4(B), for example, shows a spherical bead 24 a that has beendrawn into cavity 70 by a vacuum force pulling in a direction extendingup through lumen 86 a. The relatively large diameter of bead 24 a,compared to the diameter of lumen 86 a, as well as the bead's resistanceto significant physical deformation, prevents the bead from being suckedup into lumen 86 a. As also exemplified in FIG. 4(B), owing to theconical or funnel shape of ceiling region 74, bead 24 a becomes situatedat an upper, central area of cavity 70.

[0119] In one embodiment (not shown), as the projections are beinglowered into the ampules, with a reduced pressure established at eachprojection end region, a stream of gas is directed upwardly from abottom region of each ampule in a fashion effective to blow beads uptowards the projections. For example, a small hole can be formed throughthe bottom of each ampule. A gas-permeable membrane can cover each hole.Although permeable to gases (e.g., air), the membrane is configured toprevent beads from falling out through the holes. Flow lines cancommunicate a positive-pressure pump with the various holes. A partialcover can extend over an upper region of each ampule that permitspassage of a projection, but prevents beads from being blown past theprojections and out through the top of the ampules.

[0120] As previously noted, one embodiment of the invention contemplatesa resiliently flexible lower portion for each projection of theprojection array. With reference to projection 54 a of FIG. 7, forexample, sidewall 76 is formed of a resiliently flexible material, whilethe rest of the projection, above sidewall 76, is made of asubstantially rigid material, such as glass, plastic or metal. Thisconstruction permits the lower end region of the projection to bend asit encounters the interior contours of an ampule, such as the curved orrounded bottom region of ampule 26 a. This feature is especially usefulwhen only one or a few beads remain in an ampule, since the opening atthe projection's end region can bend to face beads gathered in a lowercentral region of the ampule.

[0121] Referring again to FIG. 1, once projections 54 a-54 f haveattracted and retained respective beads 24 a-24 f from supply 12, linearmotor 66 can vertically raise the projections, along with the retainedbeads, clear of plate 20. Rotational motor 64 can then rotate verticalshaft 60 c of frame 60 about its central axis so that the beads,retained on the projection array, are moved to a deposit location. Atthis point, the vacuum retaining force can be discontinued. For someapplications, the force of gravity, alone, will be sufficient to causeeach bead to fall from a respective cavity down to a substrate at thedeposit location. In other applications, it may be desirable to furtherurge the beads out of the cavities. In this regard, one embodimentcontemplates the establishment of an increased pressure in the manifoldabove each projection array. The pressure increase is sufficient tocause gas to flow down through the lumen of each projection, thereby“blowing” the beads out of the cavities. A pressure-control source incommunication with the manifold above each projection array can effectthe pressure increase. As shown in FIG. 1, for example, pump 102 cancommunicate with manifold 88 a via flow line 98 a; and pump 104 cancommunicate with manifold 88 b via flow line 98 b. Upon activating oneof the pumps and generating an increased pressure in a respectivemanifold, gas will flow downward through the lumens of a respectiveprojection array in a manner tending to blow any retained objects awayfrom the projection end regions.

[0122] Detection instrumentation can be included in the system of theinvention for monitoring the various operations. In one embodiment, forexample, means are provided for determining whether or not a targetobject, such as a cover member or bead, is present at the lower endregion of each projection. In an exemplary arrangement, cessation of gasflow and/or attainment of an expected (predetermined) low-pressure valuein the vacuum flow lines can be used as an indicator that eachprojection has properly engaged and attracted a target object, such thata substantially airtight seal is formed across the lower opening of eachprojection. If gas continues to flow through a vacuum line, and/or ahigher than expected pressure is measured in a vacuum line, then it ispossible that at least one of the projections failed to attract andretain a target object. A conventional gas-flow and/or pressure sensor(not shown) can be located along the flow lines for this purpose. Thesensor(s) can be read by an operator, and/or communicate with a controlcomputer. In the latter case, the computer can alert an operator to apotential error, and/or automatically initiate corrective actions.

[0123] In another exemplary arrangement, the means for determining thepresence of a target object at the lower end region of each projectionincludes a visual detection assembly. As will become apparent, thisarrangement is particularly useful in connection with target objectsthat are substantially opaque or just slightly translucent. Referringnow to FIG. 8A, for example, a bundle of light-conductive fibers,denoted generally as 112, can extend through a flow line 92 a leading toa projection array 56 a. In manifold 88 a, above the projection array,the individual fibers 112 a-112 f of bundle 112 diverge and extendtowards respective projections 54 a-54 f. Each individual fiber isarranged with a first, or “receiving,” end extending at least partiallyinto the lumen of a respective projection, and with its terminal face atthis end generally directed toward a respective cavity at a lower endregion thereof. A radiation source (not shown) can provide light, director reflected, that can pass up into each projection, toward suchreceiving ends, when the projection end region is empty and clear. Inone preferred embodiment, a diffuse light source, e.g., a fiber-opticbundle, illuminates substantially the entire upper surface of thereagent plate. Diffusely reflected light, in turn, irradiates eachprojection end region, from below. The second, or “transmitting,” end ofeach fiber is disposed in communication with a camera device (notshown). In this regard, the fibers can be bundled and supported at theirsecond end such that their terminal faces generally define a plane thatis proximate to, and generally parallel with, a planar array ofphoto-detectors of the camera device. One or a few of thephoto-detectors can be assigned to each fiber in the transmitting-endbundle. In an exemplary arrangement, the detector array is part of a CCDhaving a range of view that is generally confined to a respectivegrouping of fiber terminal-end faces.

[0124] A properly attracted and retained object will extend across asection of the projection's lower end region, thereby blocking lightfrom reaching the receiving end of a respective fiber. Consequently, thephoto-detector(s) assigned to such fiber will not receive light (abovebackground). In the absence of an object blocking a section along theprojection's terminal end region, on the other hand, light will reach arespective fiber's receiving end and will travel to its transmittingend. From the transmitting end, the light will impinge upon one or moreassigned photo-detectors. The photo-detector(s) can then produce anoutput signal that can be visualized on a CRT screen, or the like, forinspection by an operator.

[0125] The output signals can produce bright spots at pre-assignedlocations of an otherwise dark CRT screen. Thus, a bright spot on thescreen can be used to alert an operator to the absence of a targetobject at the end region of a particular projection. Alternatively, orin addition, the output signals can be transmitted through anappropriate interface to a control computer. The computer, then, canalert an operator to any projections that have apparently failed to pickup a target object, and/or automatically initiate corrective actions.

[0126] In one embodiment, a standard optical fiber having a diameter ofbetween about 30-70 micrometers, and preferably about 50 micrometers,extends into the longitudinal lumen of each projection. Suitable opticalfibers are commercially available, for example, from Edmund ScientificCo., (Barrington, N.J.). Each lumen, in this embodiment, can have adiameter of between about 230-270 micrometers, and preferably about 250micrometers. The transmitting end of each fiber, in turn, can bedisposed for communication with one or several photo-detectors of a CCDcamera. Any of numerous commercially available CCD cameras can be usedin the present invention, and suitable cameras can readily be chosen bythose skilled in the art. One particular CCD camera, contemplated foruse herein, is available commercially under the trade name PANASONICGP-KR222.

[0127] Rather than running only a single fiber into the lumen of eachprojection, as shown in FIG. 8A, it should be appreciated that anyreasonable number (e.g., 2, 3, 4, 5, or more) of fibers can be employed.Various factors that can be considered in determining an appropriatenumber of fibers to use include (i) the outer diameter of each fiber,(ii) the inner diameter of the respective lumens, (iii) the innerdiameter of the flow lines passing through the supportive frame, and(iv) the number, size and spatial configuration of the photo-detectorsin the camera device. Importantly, for those embodiments relying upon avacuum extending through each projection to attract and retain thebeads, the fibers should not substantially hinder gas flow through thevarious flow lines, manifolds and projection lumens. Preferably, anyreduction in flow rate due to the presence of the fibers is less thanabout 50%.

[0128] With further regard to the optical fibers, instead of runningeach fiber through a flow line passing through the frame structure andinto the lumens of the various projections, as illustrated in FIG. 8A,one embodiment (not shown) provides a small bore formed through an upperregion of each projection through which an end region of a fiber can bepassed. In an exemplary construction, each projection includes a plastictop portion with a metal tube extending therefrom. A small bore isdrilled through the metal part of each projection, dimensioned toreceive one end of an optical fiber. In this embodiment, each fiberforms a substantially airtight seal with its respective bore so as notto interfere with the establishment of a desired pressure (e.g., avacuum) in the system.

[0129] Rather than directing light up through each projection, thedetection system can be arranged to operate in a “reverse” manner fromthat described above. That is, the fiber ends distal from theprojections can act as “receiving” ends communicating with a lightsource. The fiber ends in the projections, on the other hand, can act as“transmitting” ends adapted to direct light down and out of eachprojection end region. In operation, prior to picking up objects withthe projections, a camera can image the projection end regions, frombelow. For example, the central frame can be rotated about an anglesufficient to pass each projection over a linear photo-detector array.Those projections that have light passing out of their lower end regionsare determined to be empty and clear—i.e., available for picking up anobject. After a pick-up operation, the camera can again image theprojection end regions. A properly picked up and retained object willblock light from reaching the camera's photo-detector array. A pick-upfailure is indicated for any projections that have light passing out oftheir lower end regions. Corrective actions can be taken, e.g., are-load attempt, in the case of a pick-up failure.

[0130] In another exemplary arrangement, illustrated in FIGS. 8B and 8C,the means for determining the presence or absence of a target object,such as a bead, at the lower end region of each projection includes oneor more cameras or other suitable image capture devices positionedbelow, but in substantially vertical alignment with, the arcuate orcircular path in which extractors 50 a and 50 b and correspondingprojection arrays 56 a and 56 b travel between the “picking up” and“releasing” steps.

[0131] In the illustrated embodiment, where two extractors are employed,two cameras 500 a and 500 b can be used. In this embodiment, afterextractor 50 a and its projection array 56 a executes a bead “pick up”operation in the position denoted by the letter A and after extractor 50b and its projection array 56 b executes a bead “release” operation inposition C, the rotation motor 64 is controlled to rotate extractors 50a and 50 b to positions B and D, respectively, where the extractors aretemporarily held while the individual projections of correspondingprojection arrays 56 a and 56 b are checked for the presence or absenceof beads. When in position B, the lower end of projection array 56 a ispositioned above, and in the field of view of, a lens 502 a of camera500 a which captures an image 506 of the lower end, depicting the endsof all of the individual projections, preferably as seen along the axisof the projections. As shown in FIG. 8C, the image is transmitted to asuitable display device 504 such as CRT or LCD display where the imageis displayed to enable an operator to visually determine if anyprojection failed to pick up a bead, or if any projection picked up morethan one bead. Similarly, when in position D, the lower end ofprojection array 56 b is in the field of view of a lens 502 b of camera500 b. In this case, the image captured by camera 500 b and displayed onthe monitor is used to determine if any projection of projection array56 b failed to release a bead. By looking at the exemplary image 506 onthe display device in FIG. 8C it can easily be seen that that each ofthe projections, except the one in row 2, column 2 contain a bead. Itshould be noted that the display device may be part of the image capturedevice, or may be a separate unit in communication therewith.

[0132] If the check step performed with cameras 500 a and 500 b revealsthat any projection of projection array 56 a failed to pick up a bead inposition A, or that any projection of projection array 56 b failed torelease a bead in position C, rotation motor 64 is controlled to rotateextractors 50 a and 50 b back to positions A and C, respectively, wherethe corresponding pick up and/or release step is again executed, asrequired. Afterward, projection arrays 56 a and 56 b are again rotatedto positions B and D, respectively, where they are once again checkedfor the presence or absence of beads by cameras 500 a and 500 b beforecontinuing to positions C and A, respectively.

[0133] Although, in the illustrated embodiment, each camera ispositioned about 90° between the pick up and release positions, this isnot necessary. It should be appreciated that the cameras may bepositioned at other locations along the arcuate travel path. Forexample, one camera may be offset 45° in the counterclockwise directionfrom position A while the other camera is offset the same degree in thesame direction relative to position C.

[0134] It should also be appreciated that more or less than two camerasmay be employed, depending on the number of extractors used. Forexample, in another embodiment of the invention where only a singleextractor is used, only a single camera, located at either position B orD, need be used. In this case, the extractor will move back and forthalong an arcuate path defined by either ABC or ADC, depending on wherethe camera is located. Thus, the single camera will perform both thecheck after pick up and the check after release. In other embodiments,where three or more extractors are used, two or more cameras may beemployed.

[0135] As previously mentioned, the attracted and retained beads can bemoved to a deposit position whereat the beads can be released. In oneembodiment, for example, the deposit location is over a substrate, suchas a micro-plate or card, having a plurality of bead-receivinglocations. FIG. 1 shows, for example, a substrate, denoted as 122,having a plurality of spaced-apart wells, such as 124 a-124 f, forreceiving and holding beads.

[0136] The receiving wells of substrate 122 can be configured foralignment with the projections 54 a-54 f, 54 g-54 l of projection arrays56 a, 56 b. In this regard, wells 124 a-124 f can be formed with thesame center-to-center spacing as projections 54 a-54 f, 54 g-54 l. Inone particular embodiment, a bead-receiving substrate is provided as aninjection-molded plate, or tray, made of any suitable material, such asacrylic, polycarbonate, polypropylene, polysulfone, or the like.Preferably, the length and width of the tray conform to the commonlyused standard of 5.03″×3.37″ (127.8 mm and 85.5 mm), although otherouter dimensions can be used. A regular array of depressions, or wells,are provided in the tray for separately receiving and holding reagentbeads dropped from above. For example, the instant embodimentcontemplates a 16×24 array of wells integrally formed with the tray,with adjacent wells spaced apart about 4.50 mm center-to-center. Eachwell, in this embodiment, has an interior region, or lumen, that issubstantially square in horizontal cross-section, and a bottom or floorregion that is generally flat. It should be appreciated, however, thatwells of any desired geometrical configuration (e.g., oval, square,rectangular, triangular, etc.) can be used. Similarly, the wells may beof any desired shape when viewed along their longitudinal axes, e.g.,straight, tapered or other shape. For the square wells of the presentembodiment, the four sidewalls of each well are provided with a slightinward taper (i.e., the distance between opposing sidewalls continuouslydecreases) along the direction extending from the wells upper, receivingend toward the floor region. Preferred dimensions for each well in thisembodiment are as follows: (i) about 1 mm in depth (top to bottom); (ii)about 1 mm×1 mm across an uppermost opening; and (iii) about 0.50mm×0.50 mm across a flat, bottom floor region.

[0137] The depending projections of an extractor, intended for use withthe just-described tray, can similarly be arranged in a 16×24 array,with adjacent projections spaced apart about 4.50 mm center-to-center.By this construction, the extractor can be positioned over the 16×24array of wells in the tray, with the two arrays in alignment. In use, aplurality of beads retained by the extractor can be deposited directlyinto the wells of the tray. For example, a plurality of retained beadson such a projection array can be lowered into close proximity withrespective openings of the well array. From this position, the beads canbe released from the projections, in a substantially simultaneousfashion, so that each bead falls into a respective well.

[0138] In another embodiment, a generally square micro-card, about1″×1″, is provided with a 32×32 array of wells. As with the previousembodiment, each well of the array is formed with a substantially squarehorizontal cross-section, and a generally flat bottom or floor region.Again, it should be noted that other well configurations can be used.Preferred dimensions for each well, according to this embodiment, are asfollows: (i) about 1 mm in depth (top to bottom); (ii) about 0.60mm×0.60 mm across an uppermost opening; and (iii) about 0.35 mm×0.35 mmacross a bottom floor region. Downwardly convergent (tapered) sidewallsextend between the top opening and floor of each well. Adjacent wells inthe array are spaced about 1-2 mm apart (center-to-center), andpreferably about 1.50 mm. So constructed, each well can hold, forexample, up to three substantially spherical reagent beads, each havinga diameter of between about 275-325 micrometers, and preferably about300 micrometers.

[0139] An extractor, suitable for use with the just-describedmicro-card, can be provided with an array of projections disposed in anarray that is complementary to the array of wells in the card,permitting direct alignment of each of the projection arrays with thearray of wells.

[0140] Instead of depositing the beads directly onto a substrate, asdescribed above, one embodiment provides a means for guiding orchanneling each bead, once released from a projection end region, to arespective receiving location on the substrate. Such means can include,for example, a conduit or channel assembly adapted for positioningbetween the projection array and substrate. Referring to the embodimentof FIG. 1, for example, a conduit assembly, indicated generally at 126,includes a plurality of conduits 128 a-128 f in a support structure 130.Support structure 130 maintains the conduits in fixed, spaced relationto one another. In one embodiment, the support structure takes the formof a frame, or rack, into which individual conduits can be secured(e.g., snap fit). In another embodiment, the conduits are integrallyformed with the support structure. For example, the conduit assembly canbe constructed of plastic using an injection molding process; or eachconduit can be formed by boring through a block of material, such asglass, plastic, metal, or the like.

[0141] The top of conduit assembly 126 is provided with an array ofopenings for receiving beads that have been released from a projectionarray, such as 56 a or 56 b. In a preferred embodiment, the conduitupper-opening array is configured for alignment with each of theprojection arrays. In this regard, the upper openings of conduitassembly 126 and the projections 54 a-54 f, 54 g-54 l of each projectionarray 56 a, 56 b can be arranged with substantially the same pitch(center-to-center spacing). The bottom of conduit assembly 126 providesan array of openings through which beads can egress. The conduitlower-opening array can be configured for alignment with the array ofwells of the substrate. For example, the openings at the bottom ofconduit assembly 126 and the wells 124 a-124 f of substrate 122 can beformed with substantially the same pitch.

[0142] In order to facilitate passing of a released bead from aprojection end region down into a conduit positioned thereunder (i.e.,ease the tolerance of bead delivery by the extractor), the upper end ofeach conduit 128 a-128 f can be formed with an expanded, orenlarged-diameter, opening. In one embodiment, for example, each conduitupper opening is at least 150%, and preferably greater than 250%, thesize of an opening defined by the lower rim or lip of a respectiveprojection end region. To facilitate passing of a bead from a conduitdown into a respective well of a bead-receiving substrate, the loweropening of each conduit can be formed with a diameter that is generallyno larger than the upper opening of a respective receiving well. In apreferred embodiment, the lower opening of each conduit 128 a-128 f issmaller than the upper opening of a respective receiving well 124 a-124f. In an exemplary construction, each conduit lower opening is betweenabout 40-95%, and preferably about 70%, the size of the opening of arespective receiving well. For example, a generally circular loweropening of a conduit, having a diameter of about 400 micrometers, can bepositioned over a substantially square receiving well having an upperopening measuring about 600×600 micrometers.

[0143] From the above discussion, it should be appreciated that it willoften be advantageous to utilize a conduit assembly wherein each conduithas a large upper opening and a small lower opening (relative to oneanother). In one embodiment, for example, each conduit upper opening hasa diameter of between about 1 mm-10 mm, and each lower opening has adiameter of less than 1 mm. In one particular construction, each largeopening has a diameter of between about 1-6 mm; and preferably about 2mm; and each small opening has a diameter of between about 0.25-0.75 mm,and preferably about 0.40 mm.

[0144] With continuing reference to FIG. 1, between its upper and lowerends, each conduit 128 a-128 f of conduit assembly 126 can be shaped topromote ready passage of a bead therethrough and down onto a substrate,such as 122, thereunder. One embodiment, for example, providesdownwardly convergent (tapered) sidewalls between the upper and loweropenings of each conduit. In the exemplary arrangement of FIG. 1, thesidewalls of each conduit are generally straight along the longitudinaldirection, defining generally cone-shaped conduits. In another exemplaryarrangement, the sidewalls are curved along the longitudinal direction,defining generally horn-shaped conduits.

[0145] As previously indicated, it is often advantageous to utilize aconduit assembly having an upper-opening array configured withsubstantially the same pitch as the projection array, and further havinga lower-opening array configured with substantially the same pitch asthe receiving-well array of a substrate. Thus, in systems where thepitch of both the projection and receiving-well arrays are substantiallythe same, the pitch of the conduit upper- and lower-opening arrays willbe about equal. For example, FIG. 1 shows an embodiment wherein each of(i) the projection arrays, (ii) the receiving-well array, and (iii) theconduit upper- and lower-opening arrays all have substantially the samecenter-to-center spacing.

[0146] In systems where the pitch of the projection and receiving-wellarrays differ, on the other hand, it will often be advantageous toutilize a conduit assembly having upper- and lower-opening arrays thatdiffer in pitch, as well. In one exemplary system of this type, theconduit lower-opening array is provided with a center-to-center pitchthat is smaller than that of the conduit upper-opening array. FIG. 9shows, for example, an embodiment much like that of FIG. 1, except thatreceiving wells 124 a′-124 f′ of substrate 122′ are arranged in an arrayhaving a pitch that is substantially smaller than that of the projectionarrays 56 a, 56 b. Consequently, the upper- and lower-opening arrays ofconduit assembly 126′, in this embodiment, differ in pitch in a similarfashion. For example, the center-to-center pitch of the lower-openingarray can be between about {fraction (1/2)} to {fraction (1/4)} that ofthe upper-opening array. In one particular embodiment, thecenter-to-center pitch of the lower-opening array is about {fraction(1/3)} that of the upper-opening array.

[0147] With further regard to shape, it should be noted that each ofconduits 128 a′-128 f′ of FIG. 9 is curved along its longitudinaldirection such that it roughly defines an “S” shape. In anotherembodiment, one or more of the conduits are substantially straight. Inthis regard, attention is drawn to conduit assembly 126″ of FIGS.10(A)-10(C). In this arrangement, a 10×10 array of conduits, such as at128″, are formed in a support structure, such as block 130″. Block 130″,in turn, is situated over a micro-card 122″ having a 10×10 array ofreceiving wells that are aligned with the conduit assembly'slower-opening array. The conduit assembly's upper-opening array, asdepicted in FIG. 10(B), can have, for example, 4 mm diameter openingsdisposed at a 6 mm pitch, and the lower-opening array, shown in FIG.10(C) can have 0.4 mm diameter openings disposed at a 1.5 mm pitch.

[0148] The conduit assembly can be manually placed over thebead-receiving substrate, or it can be placed over the substrate in anautomated fashion. In either case, it will often be helpful to includein the system a means for registering the bead-receiving locations ofthe substrate with the lower-opening array of the conduit assembly. Inone embodiment, indexing pins, such as at 132,134 in FIG. 1, dependingfrom the lower side of conduit assembly 126, can assist in registeringthe wells of micro-plate 122 with the lower-opening array of conduitassembly 126. Particularly, each indexing pin 132, 134 is alignable witha respective indexing bore, such as 136, 138, formed through acorresponding region of substrate 122. Insertion of the indexing pins inthe indexing bores substantially aligns the lower-opening array of theconduit assembly with the array of wells of the micro-card.

[0149] With further regard to placement of the conduit assembly over asubstrate, one embodiment contemplates the inclusion of a conventionalmotor or pneumatic lifter in the system, such as at 140 and 140′ inFIGS. 1 and 9, respectively. Lifter 140 is adapted to raise and lowerthe conduit array along a generally vertical pathway. Those skilled inthe art can readily select a suitable lifter from the devices that areavailable from commercial sources. Preferably, lifter 140 is adapted foroperation under the direction of a control computer (not shown).

[0150] In another embodiment, a parallelogram linkage assembly supportsa conduit assembly for reciprocal movement between a raised position anda lowered position. FIG. 11, for example, shows an exemplaryparallelogram linkage assembly, indicated generally as 144, supportingconduit assembly 126″ for such movement. In the illustrated arrangement,first and second side links, denoted respectively as 146 and 148, areprovided along one side of linkage assembly 144. The lower ends of sidelinks 146, 148 are pivotally attached at respective, spaced-apartlocations, or pivot points, 150, 152 proximate a supportive surface 154,and pivotally attached at their upper ends, in a similarly spaced-apartfashion, at pivot points 156, 158 along a horizontal link 160. By thisconstruction, horizontal link 160 can be moved up and down along agenerally arcuate pathway between a raised position, as depicted inbroken lines, and a lowered position, as shown in solid lines. Althoughnot visible in FIG. 11, an additional pair of side links, like sidelinks 146 and 148, are provided on the opposite side of linkage assembly144. A substrate holding area, indicated generally as 164, is providedadjacent to parallelogram linkage assembly 144 for receiving and holdinga bead-receiving substrate, such as 122″. Conduit assembly 126″ becomespositioned over substrate 122″ when linkage assembly 144 is at itslowered position (solid lines).

[0151] Indexing pins 132″, 134″ are adapted to mate with respectiveindexing bores 136″, 138″ in substrate 122″ to assist in aligning thelower-opening array of conduit assembly 126″ with the well array ofsubstrate 122″. Details of a similar indexing arrangement are shown inFIGS. 12(A)-12(B). Here, one indexing pin, such as 132′″, can be alignedwith a bore 136′″ through micro-card 122′″, and a second pin 134′″ canbe aligned with slot 138′″ formed in micro-card 122′″. Returning to theview of FIG. 11, a passageway 166 can open into a central region of thesubstrate holding area 164. By connecting conduit 166 to a remotepressure-control source, a vacuum can be established reaching to, anddrawing upon, the lower surface of a bead-receiving substrate 122″,thereby maintaining the substrate in a seated position.

[0152] It should be noted that there are other ways of positioning theconduit assembly relative to the micro-card. For example, a lineararrangement of two motors may be used. In this arrangement, one motorcan be used to move the conduit assembly into place over the micro-card.The other motor can then be used to push the micro-card into the conduitassembly to connect them after the conduit assembly has been moved intoplace.

[0153] With additional reference to the perspective view of FIG. 13, aplurality of parallelogram linkage assemblies, such as 144, eachcarrying a respective conduit assembly 126′, can be seen in combinationwith a carousel arrangement, denoted generally as 168. Rotational motionof carousel 168 causes the various linkage assemblies to revolve aboutthe carousel's central axis “A”. Preferably, such motion of the carouselis carried out under the direction of a control computer (not shown).Each conduit assembly is disposed along a region of a respectivehorizontal link 160 lying radially outward of axis “A”. In oneembodiment, for example, each horizontal link is rigidly attached to, orintegrally formed with, a frame structure having a central opening (notvisible in FIG. 13) configured to receive and support a respectiveconduit assembly. The other end of each horizontal link 160 rigidlyattaches to, or is integrally formed with, an elongated arm 172 thatextends in the direction of the carousel's rotational axis “A,” reachingto and engaging a rail 174 running along the inner region of thecarousel's supportive surface. As best seen in FIG. 11, rail 174provides a bearing surface 178, further described below, along whicheach linkage assembly 144 can ride as it is advanced by carousel 168. Inthis regard, elongated arm 172 includes a downwardly angled, terminalbend 180 adapted to slide along bearing surface 178. A bearing materialcan be attached to bend 180 along a region confronting bearing surface178. Preferably, the bearing material is selected to provide a contactinterface with low sliding friction. For example, FIG. 11 illustrates aboss 182 formed of a low-friction material, such aspolytetrafluroethylene (PTFE) or the like, bonded to bend 180 at aregion adjacent bearing surface 178.

[0154] As mentioned above, and with particular reference to theperspective view of FIG. 13, it can be seen that rail 174 runs along aninner region of the carousel's supportive surface 170. Moreparticularly, the bearing surface 178 of rail 174 includes (i) a firstarcuate section disposed a first distance R1 from rotational axis “A” ata first vertical height H1 above the carousel's supportive surface; and(ii) a second arcuate section disposed a second distance R2 from axis“A,” shorter than distance R1, at a second vertical height H2, higherthan vertical height H1. The configuration of each such arcuate sectionis nearly that of a semicircle, measuring between about 60-85 degrees.Transition sections, as at 183 and 184, bridge the first and secondarcuate sections. Together, the first and second arcuate sections, andthe transition sections, provide a continuous, bearing surface,appearing roughly oblong in top plan view (not shown).

[0155] In operation, as each parallelogram linkage assembly 144 isadvanced along the first arcuate section of rail 174, a respectiveconduit assembly 126′ will be located at the lowered position, directlyover a substrate 122′. As each parallelogram linkage assembly is movedalong the second arcuate section, its respective conduit assembly willlocate at the raised position, above and offset from the substrate.

[0156] Detection instrumentation can be included in the system of theinvention for determining the presence of a bead at target locations ofa bead-receiving substrate, such as in the wells of a micro-card. In oneembodiment, all beads carrying a particular reagent are formed todisplay a unique, pre-assigned color. The detection instrumentation, inthis embodiment, is adapted to inspect each target well for a bead ofsuch color. In the exemplary arrangement of FIG. 14, an illuminationsource, such as laser 186, directs an expanding radiation beam 188towards a lens 190. Lens 190 focuses the beam to irradiate theupper-opening array of conduit assembly 126″ so that a fraction of thebeam passes down through each conduit to the wells of plate 122″. Uponstriking each well, and its contents (if any), a retro-beam 192 ofreflected light travels back up through each conduit, towards lens 190.To facilitate passage of the retro-beam through the conduits, eachconduit can have a reflective inner surface, e.g., a highly polishedmetallic surface. Lens 190 focuses the retro-beam 192 to pass through anaperture 193 and fall upon a collimating lens 194 which, in turn,directs the beam to a color filter 196. Color filter 196 only permitslight of a designated wavelength (or range) to pass to a sensor array ofan adjacent camera device, such as CCD camera 198. Each well ofmicro-card 122″ is assigned to one or a few photo-detectors of the CCDcamera 198. Target wells that have been successfully loaded with a beadof the designated color will provide a retro-beam capable of passingthrough the color filter and striking respective photo-detectors of theCCD camera. The photo-detectors, in turn, can communicate an outputsignal for visualization on a video screen and/or transmission via anappropriate interface to a computer. In either case, a positive signalis indicative of successful loading. Any target well(s) failing to holda bead of the designated color, on the other hand, will not be able togenerate a retro-beam capable of reaching the CCD camera. Accordingly,the photo-detector(s) assigned to such well(s) will not produce a signaland a loading failure is indicated. A new loading attempt can then bemade, or the card can be rejected.

[0157] Rather than relying only upon reflected light to provide aretro-beam from each well, the coating on each bead can be of a typethat fluoresces upon being illuminated with light of a certainwavelength. In this way, each bead can generate fluorescent emissions ofa particular, pre-assigned color indicative of the reagent that itcarries.

[0158] In another embodiment, similar to that of FIG. 14 (describedabove), an array of optical fibers communicates an illuminating beamwith a plurality of target locations of a bead-receiving substrate, andfurther communicates a retro-beam leaving each target location with alight-sensitive camera device. As shown in FIG. 15, for example, anexpanding beam 188′ emanating from laser a 186′ is directed through alens 190′ onto the terminal ends of an array of optical fibers,including fibers 202. The other terminal end of each fiber is disposedabove, or in, a respective conduit of conduit assembly 126″. In oneparticular arrangement, each fiber extends down through a respectiveconduit to a location slightly above a respective bead-receiving well. Aretro-beam, leaving each well, can travel up through its respectivefiber towards lens 190′. Lens 190′ focuses the retro-beam 192′ to passthrough an aperture 193′ and fall upon a collimating lens 194′ that, inturn, directs the beam to a color filter 196′. As with the previousembodiment, color filter 196′ only permits light of a designatedwavelength (or range) to pass to a sensor array of an adjacent cameradevice, such as CCD camera 198′. Additional details are substantiallylike those of the previous embodiment.

[0159] In certain applications, it may be desirable to detect beads ofdifferent colors, e.g., blue beads, red beads and green beads. To thisend, either of the above-described detection assemblies (FIGS. 14 and15) can be provided with a plurality of color filters, with each filterbeing independently movable in and out of the retro-beam path prior tothe camera device. By selecting an appropriate filter, and moving itinto position for interception of the retro-beam, beads of a particularcolor can be detected. Another embodiment contemplates the use ofmultiple, separate detection assemblies, each being configured to detectbeads of a particular color. The detection assemblies can besubstantially alike, except that each includes a uniquely coloredfilter. For example, one detection assembly can include a filter adaptedfor the detection of blue beads, another can include a filter fordetecting red beads, and a third can have a filter for detecting greenbeads. The different detection assemblies can be arranged in seriesalong a conveyor apparatus carrying bead-receiving substrates.

[0160] The broken-line rectangle 204 surrounding certain of thedetection assembly components in FIGS. 14 and 15 schematicallyrepresents a housing or case within which the detection assemblycomponents can be mounted. In one preferred embodiment, the housing isadapted for reciprocal linear movement along a generally verticalpathway over a conduit assembly. With particular reference to theembodiment of FIG. 15, for example, laser 186′, lenses 190′ and 194′,aperture 193′, color filter 196′ and CCD camera 198′ can all be mountedin housing 204. The upper region of each optical fiber 202 is alsomounted in the housing, with the terminal end of each fiber facing lens190′. The lower ends of the optical fibers project out through thebottom wall of housing 204. The projecting fiber ends are arranged in anarray complementary to the conduit upper-opening array. By thisconstruction, the detection assembly can be lowered over a conduitassembly and micro-card, such as 126″ and 122″, in a fashion permittingeach fiber end to enter, and extend down into, a respective conduit.Once the detection has been completed, the detection assembly can beraised and another conduit assembly/micro-card can be moved intoposition under the detection assembly.

[0161] Instead of inspecting for the presence of beads in the wells of asubstrate while a conduit assembly is lowered thereover, as describedabove, one embodiment contemplates removal (lifting) of the conduitassembly prior to detection. In this embodiment, the detection assemblyirradiates the wells directly, and detects for the presence of beads onthe basis of color.

[0162] Another feature of the present invention provides a system forcovering an array of wells formed in a substrate, such as a micro-plateor card. According to one embodiment, depicted in the side-sectionalview of FIG. 16(A), the system includes a continuous web of a covermaterial, denoted as 212, mounted for movement from a supply position,such as idler reel 214, to a take-up position, such as driven reel 216.Shearing blades 218 are mounted on the lower face of a movable piston222 for reciprocal linear motion along a direction substantially normalto the web for cutting out a portion of the cover material 212 at aregion between the supply position 214 and take-up position 216. Aresiliently compliant, generally planar surface, indicated at 220, isprovided on the lower face of piston 222 along a region between blades218 for pressing the cover material against the upper surface of asubstrate, such as micro-card 122″.

[0163] Indexing pins 232, 234, depending from the lower face of piston222, can register with indexing bores 136″,138″ of the substrate 122″ toorient the shearing blade 218 thereover for effecting a desired cut inweb 212. Although not visible in the sectional view of FIG. 16(A), theshearing blades collectively provide a cutting edge defining aquadrilateral, such as a square or rectangle. In this regard, FIG. 16(B)illustrates sequential cuts 224, 226 made in web 212 by shearing blades218, with each cut having (i) two sides substantially parallel to theside edges of the web and (ii) two sides substantially normal to theside edges of the web.

[0164] Any suitable cover material can be utilized. Preferred materialsare substantially chemically inert with the reagents placed in thewells. One embodiment contemplates the use of a cover material that iscapable of forming a substantially fluid-tight seal with the uppersurface of a multi-well tray, or appropriate regions thereof (e.g., anupstanding rim or lip about the opening of each well). Such a seal canbe effected, for example, using conventional adhesives and/or heatsealing techniques. Suitable heat-sealable materials include, forexample, polymeric films, such as polystyrene, polyester, polypropyleneand/or polyethylene films. Such materials are available commercially,for example, from Polyfiltronics, Inc. (Rockland, Mass.) and AdvancedBiotechnologies (Epsom, Surrey England UK). One embodiment contemplatesthe use of a substantially clear polymeric film, e.g., between about0.05-0.50 millimeters thick, that permits optical measurement ofreactions taking place in the covered wells. In this regard, it will berecalled that the present invention contemplates real timefluorescence-based measurements of nucleic acid amplification products(such as PCR). Generally, in such a technique, an excitation beam isdirected through a sealing cover sheet into each of a plurality offluorescent mixtures separately contained in an array of reaction wells,wherein the beam has appropriate energy to excite the fluorescentcenters in each mixture. Measurement of the fluorescence intensityindicates, in real time, the progress of each reaction. For purposes ofpermitting such real time monitoring, each sheet in this embodiment isformed of a heat-sealable material that is transparent, or at leasttransparent at the excitation and measurement wavelength(s). Onesuitable heat-sealable sheet, in this regard, is a co-laminate ofpolypropylene and polyethylene. A heatable platen (not shown) can beused to engage the sheet, once cut and placed over an array of wells,and to apply heat so that the sheet bonds to the substrate.

[0165] At this point, attention is directed to the perspective view ofFIG. 13, wherein a number of the above-described features of theinvention can be seen embodied in a high-throughput system forfabricating an array of beads on a micro-plate or card. Generally, alinear conveyor 252 transports, in serial fashion, empty micro-cards122′ from a supply area 254 to a position adjacent a first robot 260. Asthe robot 260 picks up an empty card 122′ from the conveyor 252, arotatable carousel 168 advances a platform 154 and an associated,movable conduit assembly 126′ to a location also adjacent the robot 260.Notably, the conduit assembly 126′ is disposed at a raised position,above and vertically offset from a substrate-holding area 164 of theplatform 154. The robot 260 places the card 122′ at the unoccupiedsubstrate-holding area 164, and the carousel 168 rotates to advance thecard 122′ to a position adjacent a scanning assembly 264. With theconduit assembly 126′ still raised, the scanning assembly 264, e.g., abar-code reader, scans a label on the side of the card 122′. Thisoperation can serve, for example, to ensure that the card has beenproperly placed at the substrate-holding area and to read identifyinginformation into a control computer (not shown). Next, a parallelogramlinkage assembly 144 lowers the conduit assembly 126′ to a positiondirectly over the card 122′, with a lower-opening array of the conduitassembly 126′ aligned with a complementary array of wells in the card122′. The card 122′ is then advanced to a loading position adjacent abead dispensing arrangement, as at 8, which can be constructedsubstantially as shown in FIG. 9. The dispensing arrangement 8 isoperable to pick up a plurality of beads from a reagent plate 20 and,upon rotating about 180°, to deposit the beads into the micro-card 122′via the conduit assembly 126′, as previously described. Furtherregarding the dispensing arrangement 8, it should be appreciated thatwhile one bead extractor 50 a deposits a set of beads into the wells ofa micro-card, the other extractor 50 b can simultaneously pick upanother set of beads from the reagent plate 20 for placement in the nextcard advanced to the loading position. This operation can continue untilall of the empty cards have been filled and/or the supply of reagentbeads has been exhausted.

[0166] Having received beads from the dispensing arrangement 8, the card122′ is then advanced to a position below a detection assembly 204,e.g., like that of FIG. 15, that inspects each well of the card 122′ forthe presence of a bead. As the card 122′ leaves the detection assembly204, the conduit assembly 126′ is returned to the raised position, andthe card 122′ is presented to a sealer 268 that places a cover, such asan optically clear membrane, over the wells. The sealer can beconstructed, for example, substantially as shown in FIG. 16(A). A secondcamera, as at 272, then inspects the card 122′ to ensure properplacement of the cover. Finally, the card 122′ is advanced to a secondrobot 274, located between the carousel 168 and conveyor 252, whichlifts the card 122′ from the substrate-holding area 164. If theinspection operations indicate that the card 122′ has been properlyloaded with beads and effectively sealed, the card 122′ is then placedback on the linear conveyor 252 and transported to a storage location280. If a failure in either of these regards has been indicated, on theother hand, the robot 274 can instead deposit the card 122′ in a rejectbin, as at 284.

[0167] A control computer (not shown) can integrate the operation of thevarious assemblies, for example through a program written in an eventdriven language such as LABVIEW® or LABWINDOWS® (National InstrumentsCorp., Austin, Tex.). In particular, the LABVIEW software provides ahigh level graphical programming environment for controllinginstruments. U.S. Pat. Nos. 4,901,221; 4,914,568; 5,291,587; 5,301,301;5,301,336; and 5,481,741 (each expressly incorporated herein byreference) disclose various aspects of the LABVIEW graphical programmingand development system. The graphical programming environment disclosedin these patents allows a user to define programs or routines by blockdiagrams, or “virtual instruments.” As this is done, machine languageinstructions are automatically constructed which characterize anexecution procedure corresponding to the displayed procedure. Interfacecards for communicating the computer with the motor controllers are alsoavailable commercially, e.g., from National Instruments Corp.

[0168] A further aspect of the invention provides a hand-held unit forsimultaneously picking up a plurality of reagent-carrying beads anddepositing the beads at a desired location. An exemplary arrangement ofone such device, denoted generally by the reference numeral 350, isdepicted in FIGS. 17(A)-17(B). Here, a rectangular frame member 360,having substantially planar upper and lower broad surfaces, is providedwith a handle 363 rigidly attached thereto. Handle 363 is roughly U- orarch-shaped and oriented over frame 360 so as to provide a gap 365between its central region and the upper surface of frame 360.Preferably, gap 365 is dimensioned to accommodate the fingers of anoperator's hand upon grasping handle 363.

[0169] A generally rectangular support 358, also having substantiallyplanar upper and lower broad surfaces, is attached to an underside offrame 360. Frame 360 and support 358 are disposed in fixed, spacedrelation, with their confronting surfaces generally parallel to oneanother. A plurality of projections, such as 354, depend from the lowersurface of support 358. Preferably, the projections are arranged in anarray, such as an 8×12, 16×24, or 32×32 array, although other layoutsare possible. Each of the projections has a cavity at a lower end regionthereof, adapted to receive a bead, as previously described.

[0170] Elongated legs 367, upon which the unit can rest, extenddownwardly from respective corner regions of frame 360. Preferably, thelegs are of a type permitting adjustments to the height of the unit. Forexample, each leg can have threads formed about its outer circumferenceadapted for mating engagement with internal threads of respective boresformed through the frame's corner regions. A knob, such as 369, canrigidly attach to the upper end of each leg 367 to facilitate manualheight adjustments, e.g., by rotating the legs.

[0171] Upon grasping handle 363, an operator can pick up the unit 350and place it over a reagent supply, such as plate 20 of FIG. 1. Thereagent-supply locations (wells) of the plate are preferably arranged inan array having a center-to-center spacing substantially like thehand-held unit's projection array 356 so that the two arrays can bealigned. By this construction, each projection 354 of the projectionarray 356 can be lowered into a respective bead-holding well to attracta reagent bead.

[0172] An attraction source is operable at each of the projection endregions in a manner effective to draw individual beads from the supplyinto respective cavities and to releasably retain them therein. In oneembodiment, the attraction source includes a pressure-control assemblycapable of generating a reduced pressure (vacuum) at each projection endregion. With continued reference to FIGS. 17(A)-17(B), for example, achamber or manifold 388 can extend through support 358, over theprojection array 356. Each projection of the projection array can havean axially extending lumen (not shown) providing fluidic communicationbetween the cavity at its lower end region and the chamber 388 insupport 358. In this regard, the projections can be formed, for example,substantially as shown in FIGS. 4(A)-4(B) or FIG. 5. Chamber 388 isfurther disposed in fluid communication with a pressure-control source.Any suitable pressure control source can be utilized. For example, thepressure control source can be a pump, or a syringe-type device,operable in one mode to evacuate chamber, and in a second mode topressurize chamber. In one preferred arrangement, shown in FIGS.17(A)-17(B), the pressure-control source is a resiliently deformablesqueeze-type bottle 391 that is mounted to an upper side of handle 363.A connector line 393 permits fluid communication between chamber 388 andbottle 391. Upon deforming or crushing bottle 391 by, for example, ahuman hand, fluid (e.g., a gas, such as air) can be forced out, therebyeffecting a pressure increase in chamber 388 and at each projection endregion. When released, bottle 391 substantially returns to its originalshape, creating a suction or vacuum force tending to draw air out ofchamber 388. The evacuated chamber 388, in turn, generates a reducedpressure at each projection end region. To provide control over the flowof fluid between bottle 391 and chamber 388, a valve assembly, such asat 395, can be situated along flow line 393. Conveniently, athumb-depressible, spring-biased button 397 located near one end ofhandle 363, permits manual control (e.g., “on/off”) over the flow offluid through line 393.

[0173] Once beads have been attracted to, and retained in, respectivecavities of the projection array 356, the beads can be moved to adeposit location and released. For example, the hand-held unit 350 canbe placed over a bead-receiving substrate, such as micro-plate 322 ofFIG. 17(A), having a plurality of wells (e.g., 96, 384, 1,024, or more)formed therein. In a preferred embodiment, the wells are arranged with acenter-to-center spacing substantially like the projection array 356 sothat the two arrays can be aligned. Release of the beads can beaccomplished, for example, by discontinuing the retaining force. Forsome applications, the force of gravity, alone, will be sufficient tocause each bead to fall from a respective cavity down into a respectivewell. In other applications, it may be desirable to further urge thebeads out of the cavities. In this regard, one embodiment contemplatesthe establishment of an increased pressure in the chamber above theprojection array. This can be effected, for example, by pressing uponbottle 391 to further deform (crush) it, thereby forcing some of theremaining air from bottle 391 into chamber 388 and, consequently, downthrough the lumen of each projection. In this way, the beads can be“blown” out of the cavities down towards the wells.

[0174] In one embodiment, the beads are deposited directly into thewells of micro-plate 322. In another embodiment, a conduit assembly,such as 326, is utilized to guide or channel each bead into a respectivewell. In the exemplary arrangement of FIG. 17(A), conduit assembly 326includes a plurality of large openings formed along one side, arrangedin an array alignable with the projection array 356. A plurality ofsmall openings are formed in the other side of the conduit assembly 326,alignable with the array of wells in micro-plate 322. A generally cone-or funnel-shaped conduit, such as at 328, extends between each largeopening and a respective one of the small openings.

[0175] Indexing pins, such as 332 and 334, that depend from the lowerside of conduit assembly 326, can assist in registering the wells ofmicro-plate 322 with the lower-opening array of the conduit assembly.Particularly, each indexing pin is alignable with a respective indexingbore formed through a corresponding region of micro-plate 322. Insertionof the indexing pins into the indexing bores substantially aligns thelower-opening array of the conduit assembly with the array of wells ofmicro-plate.

[0176] At this point, it can be well appreciated that the beaddispensing system of the present invention offers a number of advantagesover typical liquid dispensing arrangements. For example, the volume ofeach bead can be accurately determined by measuring it off-line. Also,because beads are solid, they do not drip or splatter, thereby reducingthe likelihood of cross-contamination. Further, the bead dispensers ofthe present invention can be used to dispense multiple reagents withoutfrequent cleaning, and without a substantial risk of clogging. And,because of their high-contrast edges, the presence or absence of a beadat a selected location can be readily determined.

[0177] It is also noteworthy that the process of bead dispensing, astaught here, is less energetic than typical fluid ejection systems. Forexample, ink-jets generally eject fluid at a rate of kilohertz and at avelocity of several meters per second. The present invention, on theother hand, can be used to drop beads into wells at a rate of only oneor a few per second. Accordingly, problems associated with veryenergetic spot deposition, such as splattering, breakage, andmisdirected ejection (satellites) can generally be avoided.Notwithstanding the relatively slow rate, as compared to otherdeposition methods, the system of the present invention is comparativelyquite fast owing, among other reasons, to its highly parallel approach.

[0178] In another of its aspects, the present invention provides a fluiddistributor useful, for example, for depositing a liquid in an array ofwells of a micro-plate or card. According to one embodiment, the fluiddistributor includes a plurality of elongated conduits disposed infixed, spaced relation in a common support structure. Each conduit has alarge opening at one end and a small opening at its other end. The largeopenings are disposed in an array along one side of the supportstructure, and the small openings are disposed in an array along anopposite side of the support structure. A region of each conduitextending from a respective one of the small openings is of capillarysize, such that a liquid placed in contact with the small-opening arraycan be drawn at least partially into the conduits by capillary action.Any inner diameter which effects the desired capillary action can beutilized within the scope of this invention. For example, thecapillary-size regions can be formed with an inner diameter of less thanabout 1 mm. To further encourage the desired capillary action, thecapillary-size region of each conduit can be provided with innersidewalls that are hydrophilic.

[0179] With reference to FIGS. 18 and 19(A)-19(B), an exemplary fluiddistributor 402 is shown. An array of small openings, as at 404, areprovided on one side of distributor 402 and an array of large openings,as at 406, are provided on an opposite side. The two arrays of openingscan be arranged with a like pitch, or they can differ from one another.In the illustrated arrangement, small-opening array 404 is arranged witha substantially reduced pitch as compared to large-opening array 406. Aconduit extends between each large opening and a respective one of thesmall openings. FIG. 18 shows conduits 408 a-408 f, each havingsidewalls that taper (i.e., decrease in diameter) along the directionfrom a respective large opening to a small opening. As shown in FIGS. 18and 19(A), a groove or channel 412 extends around the small-openingarray 404. And as shown in FIGS. 18 and 19(B), an upstanding peripheralwall 414 extends around the large-opening array 406 on the opposite sideof the distributor 402.

[0180] With additional reference to FIG. 20, a vessel 418 is providedfor holding a selected fluid, as at 427. Vessel 418 is provided with abottom, sidewalls, and an open top. The sidewalls of vessel 418 areconfigured to register with channel 412 about the small-opening array404 so that each small opening can be placed in contact with the fluid427. The small openings, and a region of their respective conduits, aresized such that capillary action can draw some of the fluid into eachconduit, as at 433 in FIG. 20. The amount of fluid drawn into eachconduit will depend upon the nature of the fluid, the materialcomposition of the conduit, and the diameter of each opening and sectionof conduit thereabove. This amount can be determined experimentallyand/or calculated using principles well known to those skilled in theart. Upon lifting the fluid distributor from the vessel, the drawn-influid will remain inside the conduits. The fluid distributor 402 canthen be turned over and placed over a substrate, such as multi-wellplate 422 shown in FIGS. 21(A)-21(B) and FIG. 22. It should be notedthat the wells 423 of plate 422 are disposed in an array alignable withthe large-opening array 406 of the fluid distributor 402. Fluid 427 canthen be permitted to flow from the small-opening end to thelarge-opening end of each conduit, eventually forming a meniscus at eachend of the inverted large-opening array, as illustrated in FIG. 21(A).Upon contacting an object adjacent each large opening, such as a reagentbead 435, adhesive forces between the liquid and the object can pull thefluid out of the tubes and into the wells, as illustrated in FIG. 22.

[0181] It should be noted that vessel 418 can hold any desired fluid.For example, the fluid deposited in the bead-containing wells can be asolvent capable of dissolving and/or swelling a coating materialenveloping each bead 435, thereby providing access to a reagent core.

[0182] Also, it should be appreciated that certain disadvantages oftenassociated with the deposition of a liquid into a well already holding aliquid, such as cross-contamination due to splashing, can be avoidedusing the fluid distributor of the present invention, wherein a liquidis touched to a bead in each well.

[0183] Those skilled in the art can now appreciate from the foregoingdescription that the broad teachings of the present invention can beimplemented in a variety of forms. Therefore, while this invention hasbeen described in connection with particular embodiments and examplesthereof, the true scope of the invention should not be so limited.Various changes and modification may be made without departing from thescope of the invention, as defined by the appended claims.

It is claimed:
 1. A system for picking up a plurality of submillimeterbeads from a bead supply and transferring them to a desired location,comprising: a plurality of projections depending from a support atspaced-apart locations defining an array; a cavity formed at a lower endregion of each of said projections, each of said cavities defined by (i)a lower opening, (ii) an upper ceiling region, and (iii) a sidewallextending between said lower opening and upper ceiling region; and anattraction source, operable at said projection end regions, effective todraw beads from said supply into said cavities and to releasably retainthem therein.
 2. The system of claim 1, wherein said sidewall iscomprised, at least in part, of a resiliently flexible material.
 3. Thesystem of claim 1, wherein each cavity has a substantially constantdiameter along a region extending between its lower opening and itsupper ceiling region, such that lines extending longitudinally alongconfronting inner surfaces of each sidewall are substantially parallelto one another.
 4. The system of claim 1, wherein the diameter of saidlower opening is between about 100-1,250 micrometers and thelongitudinal length of said sidewall, from said lower opening and tosaid upper ceiling, is between about 0.50-1.25 times the diameter ofsaid lower opening.
 5. The system of claim 1, wherein the diameter ofsaid lower opening is between about 250-750 micrometers and thelongitudinal length of said sidewall, from said lower opening and tosaid upper ceiling, is between about 0.75-1.10 times the diameter ofsaid lower opening.
 6. The system of claim 1, wherein said cavity isdimensioned to receive at least half of one submillimeter bead, and topreclude entry therein of a substantial portion of a second such bead.7. The system of claim 1, further comprising a plurality of ampules forcontaining said bead supply, said ampules disposed in an array alignablewith said projection array.
 8. The system of claim 7, further comprisinga plurality of covers, each cover configured to extend over an upperopening of one of said ampules.
 9. The system of claim 8, wherein eachof said covers is a frangible membrane.
 10. The system of claim 7,wherein said support is held by a frame that is (i) adapted to pivotabout a generally vertical axis, rendering movable said projection arrayalong a generally arcuate or circular pathway, and (ii) adapted forreciprocal linear motion along a generally vertical pathway; suchmovement permitting said projections to be aligned with said ampulearray and lowered so that each projection can enter a respective one ofsaid ampules.
 11. The system of claim 7, wherein one of said ampulesholds a plurality of submillimeter beads that carry a first set ofanalyte-specific reagents, and another of said ampules holds a pluralityof submillimeter beads that carry a second set of analyte-specificreagents; said first and second reagent sets differing from each otherby at least one analyte-specific component.
 12. The system of claim 2,wherein said resiliently flexible sidewall has a generally cylindricalshape, with both an inner diameter and a longitudinal depth of betweenabout 100-1,250 micrometers.
 13. The system of claim 12, wherein saidinner diameter and longitudinal depth are between about 350-425micrometers.
 14. The system of claim 1, wherein said cavity is formed bya resiliently flexible, tubular sleeve fit over the end of a respectiveprojection, said sleeve having an overhang region extending below aterminal end of said projection defining said sidewall; and wherein saidterminal end of said projection, facing said cavity, defines said upperceiling region of said cavity.
 15. The system of claim 1, wherein eachof said projections is a capillary tube having an axial lumen extendingtherethrough, each lumen having (i) a first end that opens into arespective one of said cavities through said ceiling region, and (ii) asecond end disposed in fluid communication with a pressure-controlassembly.
 16. The system of claim 15, wherein said pressure-controlassembly includes (i) a vacuum pump operable to establish a reducedpressure within each of said lumens, said reduced pressure defining saidattraction source; and (ii) a pump operable to establish an increasedpressure within each of said lumens, said increased pressure effectiveto displace any beads retained in said cavities.
 17. The system of claim15, wherein each of said lumens has an inner diameter at said first endthat is smaller than the diameter of a respective cavity at a locationdirectly adjacent said ceiling region.
 18. The system of claim 17,wherein each of said cavities has an inner diameter at a locationdirectly adjacent said ceiling region of greater than 275 micrometers,and each of said lumens has an inner diameter at said first end ofbetween 100-275 micrometers.
 19. The system of claim 1, furthercomprising a detection system having a field of view extending alongeach of said projection end regions, and adapted to sense the presenceor absence of a bead retained in said cavities.
 20. The system of claim19, wherein said detection system includes a plurality of elongatedlight-conductive fibers, each fiber having one end that extends alongone of said projections and faces said cavity, and a second end disposedin optical communication with a camera device.
 21. The system of claim1, further comprising a conduit assembly having a plurality of conduitsfor separately channeling a plurality of submillimeter beads releasedfrom said cavities to desired locations on a substrate, said conduitshaving (i) large openings at their upper ends disposed in an arrayhaving a center-to-center pitch like that of the projection array suchthat the large openings are generally alignable thereunder, and (ii)small openings at their lower ends.
 22. The system of claim 21, whereinsaid small openings are disposed in an array having a center-to-centerpitch substantially smaller than that of the large-opening array. 23.The system of claim 22, wherein the center-to-center pitch of thesmall-opening array is reduced by a factor of at least about 3, ascompared to that of the large-opening array.
 24. The system of claim 21,wherein said substrate is a micro-card having a plurality of wellsdisposed in an array alignable under said small-opening array.
 25. Thesystem of claim 24, further comprising a detection system having a fieldof view extending into each of said conduits, and adapted to sense thepresence or absence of a bead in each well of said micro-card.
 26. Asystem for channeling a plurality of submillimeter beads to desiredlocations on a substrate, comprising: an array of micro-bead supports,each support adapted to releasably hold, from above, no more than onesubmillimeter bead; a plurality of conduits disposed under saidmicro-bead support array, said conduits having (i) large openings attheir upper ends disposed in an array having a center-to-center pitchlike that of the support array such that the large openings aregenerally alignable thereunder, and (ii) small openings at their lowerends.
 27. The system of claim 26, wherein each of said large openingshas a diameter of less than about 6 mm, and each of said small openingshas a diameter of less than about 0.6 mm.
 28. The system of claim 26,wherein said small openings are disposed in an array having acenter-to-center pitch smaller than that of the large-opening array. 29.The system of claim 28, wherein the center-to-center pitch of thesmall-opening array is reduced by a factor of at least about 3, ascompared to that of the large-opening array.
 30. The system of claim 28,wherein the center-to-center pitch of the large-opening array is greaterthan about 4 mm, and the center-to-center pitch of the small-openingarray is less than about 3 mm.
 31. The system of claim 26, furthercomprising a parallelogram linkage assembly supporting said conduitarray for reciprocal arcuate movement between a raised position and alowered position.
 32. The system of claim 31, further comprising (i) acarousel adapted for rotation about a central axis, said carousel (a)pivotally supporting said parallelogram linkage assembly for movementradially of the axis of rotation of the carousel, and (b) having asubstrate holding area adjacent to said parallelogram linkage assembly;and (ii) a stationary rail extending along an inner region of saidcarousel and having a continuous bearing surface in mechanicalcommunication with said parallelogram linkage system, said bearingsurface having (a) a region disposed a first distance from said centralaxis and at a first vertical height, whereat said conduit array assumessaid lowered position over said substrate holding area, and (b) a regiondisposed a second distance from said central axis, shorter than saidfirst distance, and at a second vertical height, higher than said firstvertical height, whereat said conduit array assumes said raisedposition.
 33. The system of claim 26, wherein said substrate is amicro-card having a plurality of wells disposed in an array alignableunder said small-opening array.
 34. The system of claim 33, wherein saidmicro-card is provided with a pair of spaced-apart indexing holes, eachbeing alignable with a respective indexing pin depending from a lowerside of said conduit array; whereupon registering said indexing pins insaid indexing holes substantially aligns said small-opening array withsaid micro-card well array.
 35. The system of claim 26, furthercomprising a detection system having a field of view extending into eachof said conduits, and adapted to sense the presence or absence of a beadon said substrate under each of said small openings.
 36. The system ofclaim 35, wherein said detection system includes a radiation sourceadapted to illuminate said substrate at locations below each of saidsmall openings; and a plurality of elongated light-conductive fibers,each fiber having (i) one end disposed to receive light traveling upthrough a respective conduit, and (ii) a second end that communicateswith a camera device.
 37. An apparatus for delivering a substance onto asubstrate, comprising: a plurality of elongated conduits disposed infixed, spaced relation in a common support structure; each of saidconduits having a large opening at one end and a small opening at itsother end; wherein said large openings are disposed in an array alongone side of said support structure, and said small openings are disposedin an array along an opposite side of said support structure; whereinsaid large-opening array is arranged with a center-to-center pitchlarger than that of the small-opening array; and wherein a region ofeach conduit extending from a respective one of said small openings isof capillary size, such that a liquid placed in contact with saidsmall-opening array can be drawn at least partially into said conduitsby way of capillary action.
 38. The apparatus of claim 37, wherein saidcapillary-size region of each conduit has an inner diameter of less thanabout 1 mm.
 39. The apparatus of claim 37, wherein said capillary-sizeregion of each conduit has inner sidewalls that are hydrophilic.
 40. Amethod for simultaneously transferring a plurality of submillimeterbeads from one location to another location, comprising: (i) picking upsimultaneously a plurality of submillimeter beads from a supply andretaining the beads at respective, spaced-apart locations defining anarray; (ii) releasing the beads, in a substantially simultaneousfashion, over a substrate having an array of separate bead-holdingregions; and (iii) individually channeling each of the released beads,in a substantially simultaneous fashion, into a respective one of saidbead-holding regions.
 41. The method of claim 40, wherein said array ofbead-holding regions has a center-to-center pitch substantially smallerthan that of the retained-bead array.
 42. The method of claim 41,wherein the center-to-center pitch of said array of bead-holding regionsis reduced by a factor of at least 3, as compared to that of theretained-bead array.
 43. The method of claim 40, wherein said supply isprovided in an array of ampules, each having a cover over an upperopening thereof; and further comprising, prior to step (i), gainingaccess to said beads by displacing, at least in part, each of saidcovers.
 44. The method of claim 40, further comprising: between steps(i) and (ii), inspecting each location of said retained-bead array forthe presence of a bead; and, if a selected number of beads are missing,picking up and retaining a bead for locations lacking a bead.
 45. Themethod of claim 40, further comprising: after step (iii), inspectingeach of said bead-holding regions for beads deposited therein.
 46. Themethod of claim 45, further comprising covering each of saidbead-holding regions with an optically clear film.
 47. The method ofclaim 40, wherein said step of picking up beads is effected byestablishing a reduced pressure at each of said locations, and said stepof releasing said beads is effected by establishing an increasedpressure at each of said locations.
 48. The system of claim 19, whereinsaid detection system includes at least one image capture devicepositioned to capture and display an image that includes the lower endregion of each of said projections to provide an indication of thepresence or absence of a bead retained in the lower end region cavity ofeach projection.
 49. The system of claim 48, wherein said detectionsystem includes a pair of image capture devices.
 50. The system of claim48, wherein the captured and displayed image further provides anindication of whether more than one bead is retained in the lower endregion cavity of any projection.